If you try to trick people you are only making a puzzle for them...people do not like to be tricked, but they do like to solve puzzles...which is why they would shout out how they think the trick works! However, people do like to be entertained. Once you entertain them, they should care less about how you do what as long as they are having a good time.
Awesome advice. This is especially good with minor effects. I recently performed the "folding dollar" trick for a friend of mine, just as "a wierd origami trick" (I know that I included the word trick, but I introduced it as if I was showing him something, not fooling him). I drew it out (at one point he almost thought that I forgot how to do it), but the reaction was quite good for such a minor miracle.