dont try and give off fake tells. they're easy to spot and they are in fact tells.
if you're acting like you have a rely bad hand and then reraise allin - you clearly have the nuts. everybody dus wen they 1st play but it's amateur.

your aim is to try and act the same way on every single hand.

one tell i often get with my friends is that a player is talking on all his hands and suddenly he stops talking and the whole table does silence. this means he is very happy with his hand - it's 2 pair or better

but i really dont think tells are the most important part of the game. most of the reading that goes on is by betting patterns. if you just keep quiet the whole time you should be alright