The Hive Mind: If you're not getting the desired effects (visuals, consciousness expansion, etc), you're probably not taking enough..
I don't know about your area, but in Australia one good tab (Hoffmans, Getafixes) of acid, will be enough to get you tripping pretty fuckin hard, while one and a half will give you a total out of body experience (which can get a little hardcore to say the least)
But saying that, on the other hand you can also eat 3 - 4 tabs of crap acid (Barts, Tim Leary's, etc) and get nothing more than you would feel off one Getafix.
Same goes for mushies.. just eat more or get better quality.