My friend once told me that LSD deconditions you - after taking it this is my favorite way of describing it. In case you dont already know, 'Conditioning' is a whole branch of psychology that essentially programs your mind to think/respond/act a certain way to an associated trigger stimuli.
I have never taken anything more than a "moderate dose" but even at that level it has the ability for your mind to assess the things you take for granted, or automatically proceed in doing without thinking. Its hard to explain because its all about your individual 'self' seeing through bullshit you should never have become attached to. A trite example would be seeing through an advertisement, or thinking you "have" to do something or buy something, and realizing you have been tricked or duped - which you promptly laugh off.
To my experience, LSD is a stimulant and feels like one, but unlike stims like amphetamine you can laugh you head off and really enjoy life. I took it in the winter once and felt extremely hot on a cold day. The stimulation can entail jaw clenching and get to point where you feel over heated mentally. Don't expect to fall asleep on it.
Talking to people is easy, but the fear that they will "find out" your on something is very realistic because it turns your eyes into saucers. Eye contact is seamless.
Lastly, if you haven't done it, and don't take a heroic dose, then get ready to realize that LSD is the most blown out of proportion thing in the drug world. You literally feel sober on the stuff at times, sans visuals, and your thought process is as clear as bottled water - it makes things more real instead of less.
Again, I disclaim I never ventured into epic doses, and I don't doubt the stories about seeing sounds and tasting colors.
Remember; If your tripping... watch your step!