We are now getting into the realms of pot odds and implied pot odds. An example of this is where your original bet is 100 to the pot size of 300 - meaning you are getting 3/1 for your money now. But in the future, your implied odds may be 2000 to the 100 or 20/1 because this represents the maximum you can win off your opponent in the hand as that is his stack size.
Pot odds are what you are getting in this instant or immediately while implied odds are the odds of the amount of chips you may win if you get to flop a monster and get an opponent's whole stack or at least a large part of it. Unfortunately, nothing is ever this straightforward in poker as the implied odds assume that nobody behind you will re-raise forcing you to fold your hand. In reality, these have to be reduced downwards to compensate for such occurrences.
As a general rule, unless you are in early position, if you are first to enter a pot in mid to late position you should come in with a raise. The reason for this is that there is a high propensity for players to fold when faced with a raise. There is a good chance that if you have a playable hand you will pick up the uncontested blinds just by raising. However, remember that if you are called it is very likely that the caller will be holding a stronger hand!
Playing the premium starting hands like the big pairs (Jacks and up) and AK are a little different. Because your starting hand is so strong you tend to have more options in the way you can play them but you should remember that with these kinds of hands you should prefer to play against few opponents rather than many. With the small pairs and suited connectors you want multiple opponents or multi way action and to see a flop cheaply as usually you will have to throw it away on the flop and as such you need to get those high implied odds.
With the bigger pairs and AK you are happy to raise and get lots of money in pre flop. Invariably any opponents will be few and they will have to be playing catch up which is difficult to do with a worse starting hand. However you should not forget that an AK is merely an Ace high and worthless unless it improves so do not get too carried away if you miss the flop and someone bets into you or raises. No pair is no pair whether you hold a 23 or an AK from the flop onwards. You should also remember that a big pair tends to only win a relatively small pot whilst the smaller pairs and suited connectors win bigger ones.
Another key area of no limit play is deception. Whenever you get to fool opponents into thinking you have a different hand from the one you are actually holding they are prone to making mistakes. If you raised pre flop they often assume that you are holding a pair or big cards so by varying your play you can mislead them at a future stage of the tournament (if they are paying attention). Because of this it can be very rewarding to play similar or the same hand in differing ways so when you raise, try and do so in a random fashion. Typically when you enter a pot your raise should be around 2 to 5 times the big blind. However if you always raise twice the big blind with Aces and 4 times with Tens, astute opponents will pick this up and use it against you at a later stage. If your table has aggressive players acting behind you and they are always re-raising you when you limp, then by all means limp next time with aces so you can re-raise them when they raise you. Similarly, if you notice people behind you are calling your raises with very weak cards, then by all means put a larger than usual raise in next time you get Aces as you are going to make them pay a premium for calling your strong hand with garbage. Perhaps what I am trying to say is that you should vary your play according to your opponents' style of play. By doing so you will confuse them as to what you may or may not be holding whilst at the same time maximizing your effectiveness against them.