I'll walk you through the really basic straight achilles lock that I learned from Steve Maxwell, because it's the one that works best from the guard for me (besides the heel hook, but that's not really a basic move and you should wait a while with that one).
I just learned this in class last week. Thanks for putting it in words. We cover so much in so little time... that it's hard for me to remember everything.
Having read through this whole thread, I just wanted to thank you for all of your tips. I know where to go when I have questions.