Hi welcome to the CardsChat forum. I am not exactly a full member yet (waiting for my freeroll club membership to be approved) but I do feel like I'm becoming more a part of this small community of poker players online. I've learned a lot so far and look forward to continuing my posting and absorption of every bit of knowledge I can obtain regarding texas hold'em. So far, my experience has been great; hopefully it will be great for you too....
As regards your question, this depends on your position and also on how many players you are playing against. In general the more players there are at table, the tighter you have to be with your hand selection at each position. Why? because if you play a large number of hands from the earliest position (known as Under the Gun), then you are setting yourself up to be re-raised by someone in front of you: so while you just limped in with your poor hand intending to see the flop (because even the poorest starting hand can become the nuts in poker, as we all know), you wind up being forced to fold when your hand is weak and never wind up seeing the flop anyways; so better to just fold to begin with. On the other hand, if you keep the range of hands you play very tight from early position, then you will feel more confident limping in from earliest position or even raising from that position and when someone re-raises, you will be in a great position to call the re-raise or 3-bet his re-raise (3-bet is basically the 3rd bet in a round of betting, so a raise would be the first bet, a re-raise would be a second bet, and a re-raise of the re-raise we call a 3-bet). So it is clear we should be playing tighter in earlier position and looser in late position....in later position you have fewer people in front of you who could re-raise you and so you can play a wider range of hands without worrying about being forced to fold too often.
Here is what I would recommend to a beginner playing No Limit Texas Hold'em with 9 players at a table (tournament structure...although good poker is good poker so these concepts could well apply to cash games also):
UTG: 6% of of hands
UTG+1: 8% of of hands
UTG+2: 10% of of hands
LOJACK: 14% of of hands
HIJACK: 23% of of hands
CUTOFF: 33% of of hands
BUTTON: 57% of of hands
SMALL BLIND: 75% of of hands
BIG BLIND: 100% of of hands (if there is no raise and get to see a free card)
Now if you don't know what the terms are above, then you need to start reading some books. I'd highly advise Bill Chen's "Mathematics of Poker" In the meantime here is a table I created to help you (I did a quick jobby job so please bear with the state of the artless graphics):
http://sites.google.com/site/punctual/Table_Positions.JPG?attredirects=0
Also, when I list a percentage above next to each position, that percent is the top x% of hands. Which is to say you play only the very best 6% of hands UTG. Now how are you supposed to remember which hands are in teh top 6% of all hands? Well, after a while you start to remember them....but in the meantime, I would suggest you download EQUILAB from pokerstrategy.com: it is a free program which allows you to type in 6% and it will show you which starting hands are in the top 6%...
Now of course, this is how I tend to play starting hands.....of course, every
poker game is different and if you stick too closely to the same starting hand strategy then your opponents will figure out how you think and use that against you. So, I'd say vary your play in general but stick to the above guidelines for the most part (or some similar framework....i understand that what is right for me is not right for everyone).
So the question you might ask now is what do you do with those hands? limp in? raise? go all in? well, for me, I don't like limping too much. IN general, you are rewarded for aggression in poker. So, when you have a hand that fits your position, i'd say you raise 3BB and if you are re-raised then you can decide whether to put yoru opponent all-in or to just call or even fold. A lot of these decisions come down to how stacked you are as well. In general if you fall below 15 Big Blinds, you should probably adopt an all-in or fold strategy and using the above guidelines should be fine in terms of the hands you can go all in with from each position.
So I hope that helps somewhat. I have been playing poker seriously for about 8 months now and I've learned a few things. I hope you get something useful out of this.