Watch the Aeolian Scale online guitar lesson by Bruce Arnold from Jazz Guitar for Beginners
The Aeolian scale is used over any Minor or sus4 tonal center. An A Aeolian scale A,B,C,D,E,F,G,A is the same scale as a C Major Scale. Again you want to resist the temptation to play over a A-7 chord tonal center with a C Major Scale because you are in the key of A minor not the key of C Major.
You should start working with the "Ear Training One Note Complete" book so that you can start to hear what key center a jam or piece of music is using.
This is one the hidden keys to becoming a great musician, one who uses his ear rather than his mind to play music.
Remember to think the notes or the degrees when learning the A Dorian scale and use a jam track for A-7 as a backing track so you hear the scale in the right relationship. You should of course know this scale in all keys.