Some tricks in playing poker?

Hi everyone
Because I'm a newbie in this poker world so I really appreciate if anyone can provide me some useful tricks in playing.
Sometime my others players can guest my cards exactly,I don't really know how can they know?
Hope you can help me.Thanks

I suppose you are showing tells? Tells are signs that give yourself and the strength of your cards away to the opponents. That is the reason why you seen so many poker pros wearing hats, sunglasses and putting up a expression less face! This is because they do not want to expose themselves.