That's pretty subtle, but sometimes small things like this make a big difference in your opponent's mind. There are lots of tiny ways to influence your opponent's perception of the game without saying a single word. Like Steve said, playing land is a good way to decieve an opponent into thinking you're using a mono-colored deck instead of a two-color deck, and playing only Islands on your first couple turns might bluff your opponent into believing you have a
Mana Leak 
prepared. If you've got nothing in your hand to play on turn 2 anyway, this comes as no disadvantage to you while limiting the amount of knowledge your opponent has. On turn three if you play a Plains, your opponent may need to rethink his/her strategy - "oh wait, that's Aura Servants and not Crosswinds!"
In paper Magic there are even more ways to mislead your opponent. For instance,
THIS video from the 2007 Worlds Finals shows recent Hall of Fame inductee Patrick Chapin using "the pen trick" against Uri Peleg. It's hard to catch, but as Uri declares he'll be attacking Chapin supposedly reaches toward his pen, suggesting that he'll be losing life in a moment and will have to write it down on his scoresheet. Chapin had no blockers on the board, so Uri swings in with all his creatures (which, if he were less sure of dealing damage, he wouldn't have done). Chapin had a
Bogardan Hellkite 
and was able to nullify all Uri's attackers.
