i have the same problem almost and i cant wait to see the answers given by others ..
its always when your talking and the work is there and BOOM its gone and you cant even describe it. no matter what you do or try the word is gone .
Nathan the only thing i can think of but i know i have no attention span to try myself 
. is to read the dictionary pick a word a day or two words a day and wright them down and use them in conversation