I trained for 9 months at circus school, they instilled a good routine into us.
I mainly did doubles static trapeze, but did a bit of everything. It's usually a fair stretch workout of itself.
Where/who are you training with?
I don't want to make any assumptions on your knowledge, as you haven't given any clues as to what you already know, so i'm going to repeat basics.
Daily stretching routines are essential.
Warm up and cool down before excercise. It alleviates any stiffening. You want to be looser not stiffer.
Stretch AFTER excecise, tired muscles put up less of a fight! (Stretched muscles are also more likely to suffer damage during excercise.)
Don't stretch when you have a cold.
Take it slowly, torn muscles result in the production of less stretchy scar tissue. That soreness you get from over stretching, that's probably microtears in your muscle structure.
There are probably a few glaring omissions there, I'm sure someone will jump in and add them.
There are so many poses and stretches that will increase your flexibility, it's hard to know what does what to what without a guide. It's also impossible to reccomend specifics over the internet without knowing where you are with your flexibility.
Sample a few classes and ask your aerial teachers (careful of the ones with a gymnastics background, as an extreme, I've seen the traumatic results of some truly brutal second hand russian coaching, what works on a very young girl, doesn't work on a twenty year old man it would appear! )
For aerial work, alongside yoga for flexibility, I would reccomend pilates for balancing your body posiion, giving you body awareness and strengthening your body core.
It's not what you do occasionally that makes a difference, it's that which you do everyday that brings progress.