Hi Sss23,
I'm not a medical doctor (so double-check everything with your physician, and don't interpret anything I say as medical advice) but I've done a lot of research in this area. First and foremost, if you've noticed a decline in your memory relatively recently, you need to talk to your doctor ASAP. I know that your phrasing didn't imply this, but since it didn't rule out the possibility, I want to err on the side of being responsible. If you feel like you are suffering a memory deficit relative to your typical baseline, inquire with your doctor about L-methylfolate. Basically just folic acid, but optically pure, and more bioavailable. Unsure if it boosts memory for individuals without any cognitive deficits, but works wonders for some folks (myself included).
Based purely on anecdotal evidence (my experiences and my brother's), I've found that DMAE has some mild but noticeable effects. More beneficial for concentration than for memory per se, but if you're interested in memory for the sake of exams/etc., concentration and recall have sufficiently close ties that you might want to give it a try.
DMAE is one of the ingredients in Focus-XT, and (having tried the other individual ingredients independently and in various combinations), I attribute most of the effects that I got from Focus-XT to the DMAE. If you take other stims, L-tyrosine and some B-vitamins probably aren't a bad idea to keep your catecholamines closer to decent levels. Not sure if DMAE is supposed to be taken with some choline support, but if so, the low bioavailability of choline bitartrate (in Focus-XT) makes it a less-than-optimal choice. I wasn't a big fan of the high caffeine content in Focus-XT, but that's presumably a matter of personal preference.
This post is getting kind of long, but one other notable memory-booster is vasopressin. I don't think that I can post links yet, but if you search pubmed for "vasopressin memory" you'll get a ton of hits. I'm not sure of the legal status (might be Rx-only) but worth an inquiry with your physician.
Best,
ACJ