Summary:
There is an essential difference between limit and no-limit Texas hold'em and this difference is based on the position you have at the playing table and on the value of the hands. When you are playing no-limit hold'em you will find that position is much more important than in the limit games. The explanation is quite simple actually because there is no limit so more money are involved and the goals you set depend on your position and they will have a bigger impact on you bank...
There is an essential difference between limit and no-limit Texas hold'em and this difference is based on the position you have at the playing table and on the value of the hands. When you are playing no-limit hold'em you will find that position is much more important than in the limit games. The explanation is quite simple actually because there is no limit so more money are involved and the goals you set depend on your position and they will have a bigger impact on you bankroll. If somehow you manage to get someone into a position trap you will here have a change to get that person's entire stack, not only a few more bets like in Limit hold'em.
In no-limit poker the big connectors are not to be played because they have a much lesser value overall: they can cause you to win but just small amounts of money and they can also cause you to lose greatly. If we are talking pairs, they increase their value consistently in no-limit Texas hold'em. They give you the opportunity to trap someone (especially the big pairs) and they can get you the entire bankroll of those persons or simply double the value of the pot over a betting round.
When playing no-limit you must before all keep an efficient list of all money spent by you and your opponents. Variations in the stack affect the whole hand and you must be aware of that. So pay attention to all amounts of money players have on the table and to the pot size at all times. The game here is about leaving the others with no money on the table not just about winning small pots and hands.
Let's take an example to better demonstrate how and why important the amount of money each player has on the table is so important.
Let's just say you have now $250 and another player has $25. You are playing a game with blinds of $1-$2. Your position is the small blind and the cards you have are QJ suited. Your opponent is in first position and he goes all-in. All other players consider the risk and decide to fold, as strategy requires in this case. Now, you are faced with a problem: to call and risk $24 for his $25 bet or to simply fold like the situation requires. Betting for that kind of money the almost exact amount is an unnecessary risk you should not take. If however your opponent would have an amount of $250 just like you have, then the risk can be acceptable as you were going to risk the money for 10 times their value.