Online poker offers many advantages over home or casino play. The most obvious advantage is that one can play anytime they have the time to do so, as opposed to having to round up a group of friends or drive to the casino. Another great thing about online poker is the higher pace of play - since there is no need to shuffle and deal the cards after each hand one can play as many as three times the number of hands per hour at a given table. It is also possible to play multiple tables at the same time while playing online, meaning one could potentially increase their profits several times. Finally, for those playing for real money, the rake is lower online, there is no need to toke a dealer, and many sites offer rebates/promotions to entice new players.
To start out in online poker you should probably play for play money. All of the sites out there - there are dozens - offer play money games where you can play and sign-up for free. However you may not want to sign up for more than one site when you just start out. The reason for this is that many promotional sites will offer you special bonuses or a rebate on your rake paid, called "rakeback", if you sign up through their link, but you will not be eligible to receive this if you have already signed up for play money at that particular poker site. Probably the best site to play on when you start out is Poker Stars (www.pokerstars.com). Unlike many of the other sites there are no special bonus offers available for Poker Stars, so you lose nothing for signing up there. Plus, Poker Stars has the best software and the most play money players. There are even sites online where you can sell your play money chips at Poker Stars for real money.
If you are serious about winning at online poker you should browse one of the many poker strategy sites available, including mine, or buy one of the many excellent poker books out there. I strongly recommend all of the books by the twoplustwo publishing company (www.twoplustwo.com) as they are widely regarded as the best around. Getting Started in Hold'em by Ed Miller is particularly good for the beginner. Hold'em is tough to play well and the best way to get better at the game is to find all the (good) advice you can, while ignoring everything else. Seek out and talk about poker to friends and family who you know to win at poker over the long term - but be careful, some may not be true winners but instead beneficiaries of short term luck - and read many of the great poker strategy forums out there. All this time you should be honing your game at the play money tables.
After playing for a little while at play money, you should have amassed a great deal of play chips if you have been working and reading about the game, and may want to try playing for real money online. There are tables on Poker Stars where you can play for as little as $1 buy-in no limit hold'em, and I recommend those for someone just starting out. However, if you are going to be playing for higher stakes, you would do better to play on one of the many other sites out there where you can face far weaker competition. When signing up for a site to play for real money, make sure that you do not sign up directly through the site but instead through somewhere where you can get a rebate/return on your play or special bonus for doing so. Maximizing your return on these promotional offers can get you started toward a nice online poker bankroll.