You bring up an interesting point about a poker face. Some people are easier to read than others. I like what "PoWdA" said about new players not knowing what they have, so it's pretty tough to read them

, funny, but true.
Some people naturally have a good "Poker Face" others have to work on it. I definitely believe that developing a poker face is a skill that can be learned.
One of the key's to having a good poker face is to be consistent in your actions. If you normally talk a lot or are smily and bubbly, do the same thing whether your weak or strong, betting the nuts or bluffing.
Poker Tells is a related but somewhat different topic. I'm going to start a new thread about
Poker Tells.
Jason