[edit: in retrospect, I feel like an idiot for making the post below, and wish I did not make it back then. It's besides the point.]
Note: I'm not intending to send a false signal/"game the system" or anything - rather - I'm just trying to send them the true signal of my interests/ability by doing small things in front of them (it may or may not result in a concrete example that gets in the LOR - but any chance really is good since the things you do are small anyways). This is because the LORs are usually more important than the personal statement, and there are many legit things we do that never get noticed by anyone (and consequently, adcoms will never see those things). And since professors have so little time, it is important to communicate as much information about yourself as possible in that short timeframe (information that isn't going to distract from your main points of conversation, of course).
Are there small things you do that could impress LOR-writers? I frequently bring over the textbooks from my other classes with me to meetings (not on intention though, but because I generally carry A LOT of things in my backpack), and this often makes the professor comment on the textbook in a positive way ("hey, i studied from that book too").
I also try to show them that I'm *really* trying to actively deal with my ADD (as in, actively take notes when other people would be content to simply remember what they listened, take pictures of things on the board, and even ask for permission to tape-record conversations). Again though, I do those since I actually need to do them.
Anyways, I hope that others will find the replies as helpful as I will.