Prior to moving forward in the throw. You want to steal uke's balance before trying to throw them, in every technique.

Some people advocate bending the knee. If that works for them, great. You'll never catch me doing that on purpose, as I'm an advocate of not compromising my posture and balance (unless its like a shikodachi type stance). I lower myself by lengthening my stance while keeping upright and centered.

As said, your shoulders should not be 'up' in aikido. Dropping your shoulders can be very tough. Having a seasoned senpai watch over you, and paying attention in mirrors helps.

My basic iriminage is;
-intercept and offbalance uke (uke snugly attached to my body)
-initiate and finish arm movement before uke can regain balance from initial interception - arm finishes around chest level, uke is completely off-balance (katameru)
-while maintaining uke in your center, C-step past uke's centerline then around to the far corner, while cutting arm the rest of the way down to direct where uke falls.
-In this version Iriminage is, in its basic form, a throw done with nage's whole body, not just their arm.

Hint: your shoulders should always be "dropped" from the moment you bow in, so that you cannot further "drop" them.

Hint number2: People will say "bend your knees" but really it is dropping your center by opening and relaxing your hip/groin and not even thinking about how the knees work in response to that.

my hands/arms don't go down. something to consider: it's easy to throw someone down when they are up, than throw them up, when they are down. i don't like the "face plant" approach, because if you run into someone who know how to wrestle/judo/bjj and so on, they will likely drop and go for your legs. i don't want to give them that opening. if you run into a bagua person, you are history too. but then again, if you run into bagua folks, they probably eat you alive. capoera will kick you in the head while they are down. too many openings in the "face plant" approach. i prefer my uke up on their toes the whole time until i drop him/her/it at the end.