Before you start betting in Texas Holdem, you need to consider all factors in pre-flop strategy.
Firstly, one has to consider the number of players in texas holdem poker. The more the people, the chances of someone else having a strong hand in the pocket than in a short-handed game is more likely.
If you have been playing for a long time, and find that someone is raising every hand pre-flop, then play tighter. Let him win the blinds and then play aggressive when you have a solid hand in the pocket pre flop.
Another factor is your bankroll. If you have less in the bank, you have to play cautiously and select one hand to bet on. However, with a larger bankroll, you can take you can take the high-risk, high-payout bets.
People in late position are able to influence the size of the pot more than those in early position. This is more so for pre-flop.
Depending your playing style, you may want to play more or less aggressively pre-flop. It also depends on your own style of play, and how you perceive the players around you.