Atemi practice in Aikido is very lacking from the sounds of it, where I train we do a lot of atemi, and we learn how to attack (to be an uke, well a convincing uke). All of the instructors at my school have studied striking arts from wing chung to tae kwon do and everything in between, even Indonesian silat. So we also learn how to defend against these attacks.
Go watch some classes in other martial arts i.e. kickboxing (which seems to be big now days) and if they teach so common attack that you haven't seen before, think of a way to counter them. It's simply say "I would like to learn (chose an art) could I come along and watch".
Read books about striking arts learn how they attack and learn how to counter them. Remember they're most likely to do the quick basics on the street, no fancy fly kicks or what ever, so researching with book should be fine. You don't need to do karate for 5 year to know the most common ways a karateka will attack you. I recommend Bruce Lee's Tao of Jeet Kune Do for you to read to see how a 'street fighter' will attack, as well as learning how to attack. I was amazed with this book and how much boxing there is in it you'll learn a lot.
Atemi is a major principle in Aikido and O'sensei used t a lot when he needed to. So why the teaching of atemi has not continued through the generations is beyond me.
Here are some atemi from Aikijutsu.
A mekakushi is a window shade, a curtain. The name of this strike, therefore, implies that its purpose is to interfere with your opponent's vision. This is the most common atemi in aiki, and it may be used in a great many forms. A typical style would be a quick flick of the fingers toward your opponent's eyes, forcing him to blink, while your other hand is doing something else (such as establishing a wristlock).
Mekakushi-uchi may also be executed in the same manner as the uraken-uchi of karate, with a strike to the nose — this will cause uke's eyes to water, temporarily blinding him. Remember, though, that the purpose is to distract the opponent, so you must simultaneously be doing something else with your free hand or it is not a true mekakushi-uchi.
This atemi is a punch to the floating ribs, such as that seen in ippon-dori, with the angle of attack directed to the person's opposite shoulder. There are two forms: in and yô. The first form uses nakadaka ippon-ken, with your pulse downward; the second uses seiken, with the inside of your wrist up (i.e., an uppercut). In either form, correct application will force uke to cough.
The side of knee is the target as the weapon is shûtô (although uraken may also be used). This atemi is seen in the Yamate-ryû waza Handachi Kote-mawashi. If properly executed — we don't do this in the dôjô as it damages the knee — this atemi causes uke to freeze for a full second.
During kote-gaeshi, you may continue your initial rotation far enough to permit a strike to uke's kidney with your elbow. Although many schools utilize this strike, it is not well thought of in the Yamate-ryû because you must turn away from uke's hand. (The Yamate-ryû teaches that, during a kote-gaeshi, uke's hand should always be in front of your center.)
Enter to uke's side and, with a cupped palm, strike the base of his skull. Vigorously applied, this causes death. This atemi may be used as an opening for an irimi-nage. (In the Yamate-ryû there is an applied form of Mune-tsuki Aiki-nage that uses this as the opening, and then finishes with haitô-uchi to uke's throat.)
Entering deeply to uke's side, teisho-uchi is used to strike at the bottom tip of his shoulder blade. (This is the atemi from Shômen-uchi Irimi-nage.) As was the case with inazuma, this strike will cause uke to cough if properly executed.
This atemi is used as a counter to men-tsuki. With a straight arm, swing your palm upward to strike the side of the elbow of uke's punching arm. Your hand should be twisted downward such that, at impact, your fingers are below his elbow. Properly executed, this will knock his arm across his eyes.
Turning away slightly, simultaneously strike uke's solar plexus with your right elbow and his nose with your right uraken. Your wrist must be deeply flexed, so that your forearm does not hit his chest (which would absorb much of the power of the blow). This atemi is commonly used as a lead-in for katate ude-gurami.
Written By Fredrick Lovret