That could take all day...what specifically do you want to know? I'll throw out some basics:
Organization; Yoshinkan aikido has split into many groups since, and even before, Shioda Gozo Sensei's passing so each group has developed a little differently since their departure. For example, Kushida Takashi Sensei our of Ann Arbor, Mi has added A LOT of weapons forms. I will go over some main points, but each dojo and group may have slight variations, however probably less so than the differences between most Aikikai schools.
Kamae: is very distinguishable from Aikikai. Generally there are three basic kamae based on weight distribution; 60/40, 70/30, and 80/20 with the numbers representing percentage of weight on front/rear leg respectively. The front foot is turned toes outward, as is the rear foot but to a lesser extent. If one were to bring the feet together front foot heel to rear foot ankle they would meet at a 90 degree angle known as shimoku no ashi or the 'log and bell' concept. From there the 60/40 stances is 1-1.5 feet lengths apart measured from front heel to rear toe. The 70/30 stance is 2-2.5 feet lengths apart, and the 80/20 is 3-3.5 feet lengths. The forward hand is about mid-chest high with a slight bend in the elbow making the arm almost the same curvature as a sword. Rear hand is about stomach high with the pam heel about a fist length off the belly. Both hands are in a vertical orientation to each other in the middle of your body representing a concept known as Shu Chu Ryoku or (focusing energy to the front)....this is often related to the Triangle in the triange/circle/square often represented in aikido. This stance allows the knee to lock securely to the outside of the body as the hip comes completely forward, square to the front (kamaemi). There are other stances such as Hitoemi (pronounced with 'sht' where the t is) which has the same leg orientation but the upper body is twisted so the forward shoulder is perpendicular to your uke, often inline and 'hiding' behind a weapon, or else done temporarily during certain projection throws to add a little extra movement for the projection.
O'toku. The great resolving. This is done after technique and is a set movement where uke/shi'te maintain a mental and spiritual connection with each other as they disengage and return to their start positions...often seen in many other budo's weapon pairing sets.
Zanshin: We have specific hand/body positions to represent zanshin at the conclusion of projection throws. A utilitarian purpose of this is to protect from legs/other stuff that may pop up after a throw and also helps to ensure shi'te has 'follow through' similar concept to that of a basketball player shooting a ball and not short stroking it.
Ukemi: There are many different ukemi in Yoshinkan aikido...for the most part broken down to 8 basic breakfalls.
Kihon Dosa: These are sorts/kinda like tai sabaki. Basic moves either with partner (sotai dosa) or alone (tandoku) that focus on maintaining correct body posture and control over oneself while moving and changing direction. There are about 8 of these and each one also is directly related to techniques in a systemic set called kanren waza.
Kihon Waza: you basic techniques. These are like mini-kata as they are done in a very specific manner and often taught in a step by step fashion. Techniques are named after the attack and subsequent waza; for ex. wrist grab all-direction throw from aihamni is written as katatemochi shihonage osae ichi (A).
*The person doing a technique is referred to as the Sh'te (often spelled Shite...but I find that leads to improper pronunciation!) which basically means "doer"...and the Uke attacks and receives technique.
Variations: There are #1 and #2 variations of each kihon waza. #1 var. generally mean energy goes toward uke's rear. #2 variations generally mean energy goes toward shi'te. The result is that most times #1 are irimi and #2 are tenkan....but not always. #1's are almost always done in ai hamni dachi while #2's are almost always gyaku hamni dachi. There are also distinctions made for oyo waza variations of techniques, and qualifiers such as shi'te going on one/both knees, projecting vs. pinning, etc.
Grabs: There is little or no foot movement for grabs. In #1 variations Uke will grab Shi'te rear hand/shoulder, etc with their forward hand. In #2, uke will grab shi'te front hand/lapel from gyaku hamni dachi. If its a #1, uke will pull shi'te, if its a #2 uke will push shi'te (hence the distinction of where energy is going.
Strikes: Same rules apply for stances with #1 and #2. Open hand strikes uke is shuffling in. Punch and kicks uke is cross-steping in.
Behind techniques: I won't even get into this, there is a complicated hojo dosa (preparatory movement) done for uke to get behind shi'te, then specific movements for shi'te to off balance depending if its a #1 or #2. I'll try to post a video of some techniques...hopefully with this on there.
Renzoku waza: There are continuation drills set up to enforce fluidity of movement while maintaining powerful technique. These are named after the first and last techniques in the series. For example there is a kaeshi waza continuation drill called "Hojo dosa Kokyunage" that starts with a hojo dosa (prep. movement) and ends with a kokyunage throw but has 8 reversal techniques in between. These continuation drills...and some oyo waza, are some of the times you will see uke cross step attack with open hand strikes and grabs.
Ronbun: written essays are required for tests, almost always at the yudansha level, but some teachers require it before hand.
Koto Shitsumon: You are often required to answer questions asked by the testing committee. Things such as explaining why certain things are done (for example why there is a #1 and #2 variation and where that comes from), knowledge of history and philosophy, and in particular knowledge of yourself (why you study martial arts, how you apply it to daily life, etc). Generally speaking, you want to answer questions in relation to their physical/technical, mental, and spiritual application.
Shido ho: Teaching technique is usually done at the yudansha level. My last test I spent well over 10 minutes explaining/answering questions about katatemochi shihonage osae ichi. You are expected to explain how and why techniques work, their history, etc. Answers like "extend ki" are not sufficient...you must be able to explain in technical terms what you need your body to do to make technique happen.
Hakama: Yondan and above can wear hakama, unless someone is teaching a class. Anyone teaching can wear hakama. Teaching licensees can be given to 1st kyu and above, but not all yudansha have teaching licensees.
Tests: yudansha tests run a little over an hour per person. I don't remember how long mudansha test last. I am at work and don't have my requirements on hand...can PM a couple example to you if you like at a later time.
Up until sandan, the testing candidate has the same partner for the whole test (unless there is multiple person requirement). This is for the Yoshinkan group I train with...could be different for others.
Testing, and most other things, are very formal events. That being said, everything we do has a specific purpose with training/growth value. Heavy emphasis is placed on philosophies relating to personal and spiritual growth through accomplishing difficult tasks and doing things that are hard. Specific and tedious etiquette is often enforced but is done for personal growth and training. These things are explained at instructor meetings, Kenshu classes (an advanced program..many Yoshinkan schools have something similar to this), at seminars and sometimes at regular class. Ideals are often spoken of...often referred to as "ishi" or 'watchword' or 'saying.' Things like "ken no fumo, ichi go ichi ei, shinken shobu, san sei no kiai, et al" are all philosophical or training concepts that are taught to students at all levels. We have many of these.
Weapons: This depends on the teacher. We have 97 weapons forms in our curriculum...we had many more by my teacher cut the others out and put them in a different class.
Most people say that Yoshinkan aikidoka develop effective techniques from the very beginning of their training and develop fluidity as they progress to the yudansha ranks while Aikikai people develop fluidity at the beginning of their training and develop effective techniques at the yudansha levels. In my experience this is, for the most part, true.
Yoshinkan aikido founder Shioda Gozo Sensei was promoted to 9th dan and told to start his own dojo by Ueshiba Sensei before WW2. Technically one could call Yoshinkan Aikibudo, but out of respect of Ueshiba Sensei, Shioda Sensei changed the name to Aikido in conjunction with Aikikai Honbu (actually, that's kind of an assumption on my part...I don't really know why Yoshinkan is called aikido vice aikibudo...but my story sounds good, right?).
Yoshinkan aikido is often looked at as harsh, brutish, with rigid technique lacking flow. I actually find the way technique is done as quite beautiful...I am fortunate enough to have trained in both. I trained in AAA-related Aikikai for six years, then was uchideshi at a Yoshinkan school for a bit less than a year and have trained in both since.
To re-emphasize, I am giving you information from my experiences (I'm in the military, travel a lot, and have trained at a lot of dojo not affiliated with the organizations I belong to). That being said, both Yoshinkan and Aikikai are large and hard to really pin down. Even each dojo-cho will do things a little different...let alone stylistic differences between each sub-organization. I would hazard to say one can't really call Aikikai...and to a certain extent...Yoshinkan a specific style. I will also generalize that perhaps the various Yoshinkan groups are more similar to each other than the Aikikai groups, which I would attribute to the broken-down, step by step, nature of most Yoshinkan aikido basic movements.
Want to know anything else let me know via here or PM....I work midnights and have nothing to do but type about aikido online!
Here is a clip of some kihon tandoku dosa (basic alone movements) and kihon sotai dosa (same thing, but with a partner added some resistance and weight to load up on shi'te around 1:33 into clip). He also does kanren waza, or applied technique of the basic movement. One of them is around 1:50. Ando Sensei also does a very basic continuation drill around 2:38...and some other stuff. http://www.youtube.com/watch?v=qNbiiKpuv8k
Here is a clip of a high-level aikido practitioner conducting a demonstration. Realize this is a demonstration and at a high level..not a typical class: http://www.youtube.com/watch?v=bEmpm...eature=related
I can probably post a clip of me teaching a basic Yoshinkan technique....just have to upload it to youtube first...if interested.