When looking for a new poker site, you have to take into consideration many factors. It depends what type of players you are and what your goals are.
Recreational player: if you are playing poker just for fun, then you can join pretty much any poker site. Recreational players are not really interested in the money or bankroll management. Recommended poker site: Carbon Poker
Normal player: usually poker players play not only for fun, but also for the money. If winning money is important to you, then you should try a poker site that has many weak opponents. Recommended poker sites: Titan Poker, Party Poker, 888 Poker.
High-roller: if you play on the higher stakes, then you need a poker site with much traffic. Low traffic sites won’t have many players on high stakes. If you are looking for a challenge then you have to join the top poker sites. Recommended poker sites: Pokerstars, Party Poker
Other factors to consider
Bonus: the first deposit bonus and reload bonuses are very important. Some poker sites offer greater poker bonuses, then others. If you decided to stick to one poker site, then reload bonuses are also very important. Recommended poker sites: Titan Poker, Everest Poker
Support: sometimes a good support team makes a huge difference. Poker sites known for the good support are: Party Poker and 888 Poker.
Graphics: if the visuals are important to you, then you should play on a poker site with great graphics. Recommended poker site: Carbon Poker.