Table Selection
Playing against opponents who are not as good as you is obviously very important. Carefully choosing which tables to play is clearly going to ensure you have the best chances from the start.Every poker site has a lobby showing the tables that you can join. First of all filter the tables so it only shows type of games and the stakes you want to play. Think about whether you want to play turbo tables or not, whether you want 9/10 seats (full ring - FR), 6 players (6max) or 2 players (heads up). Then make sure you can see the full tables as well - just looking for tables with spaces means you're missing out on some weak tables. It's better to spot the weak tables and join the waiting list - players are frequently leaving tables, so you rarely have to wait very long.
The most common method of table choice is the percentage of players seeing the flop. You can usually sort the order of the tables by clicking at the top of a column, so click at the top of the column marked PFR or Plrs/flop. The higher the percentage the better since if you have players seeing many flops then they're more likely to be weaker recreational players.
Look also for stack sizes - a table that has many shortstackers (ie < 20bb) isn't a good choice. At lower limits this often means they'll be poor players which is a good thing, but at the same time it's hard to play properly against such players. A table that has most players with full stacks is much more preferable, especially if most of those players have slightly less than a full stack.
For instance if you're looking for a NL10NL = No Limit, 10 indicates the stakes (ie $10 buy-in) table then the maximum buy-in is $10 - if you see a table where most of the players have amounts like $9.25 or $8.80 then that's a good thing. Firstly they've decent stack sizes, and secondly they're not automatically reloading their stacks to the maximum buy-in. This is sign of a weaker player since most regulars know that they're losing out on big pots by not keeping their stacks topped up.
If there are players with very large stacks then think about how they may have gained that stack. If it's more than three times the minimum buy-in then they're probably a strong player, while twice the minimum buy-in may mean that it's a weaker player who was lucky enough to stack someone. Don't be too scared of large stacks - join the table and watch for a few orbits how they play. If you're lucky they'll be a poor player who got lucky, and now has twice as much to lose to you!
Seat Selection
If you have the choice of several seats, then look at the stack sizes and any PokerTracker or Hold'em Manager stats you may have. Ideally you want to sit on the right of tightA player who folds most of their hands preflop, choosing only to play with stronger hole cards players since you can steal their blinds. You also want to be on the left of the weaker players so that you'll be in positionYour seat at the table in relation to the order of play. Being able to act after other players is a big advantage the majority of the time. If there's a strong player you don't want to tangle with much, then try to be directly opposite as it'll reduce any positional advantages as well as keeping them out of awkward blind stealing situations.Alternative Strategies
Looking at the other end of the Players/Flop spectrum are the ultra-tight tables. The advantages of sitting at an extremely nittyPlaying extremely tight table is that you can steal the blinds regularly (even from the cut-off and even earlier positions), and can see a made hand come from a mile away. However they're not as profitable as a table full of loose limpers.While you should never pass up a weak table, sometimes it can become quite hard to find a suitable table. An alternative option is to just sit at an empty table and let them come to you. Surprisingly often the table will fill up with weak players who are just sitting at the first available table. Sit down with a full stack will give off the signal to other regulars that you're not weak either. When the first few players sit down the hands will pass rapidly (as well as the blinds) - don't be tempted to play too quickly as you'll be creating a large Players/Flop percentage while shorthanded. It's better to play slowly and give the table a chance to fill up before it becomes a target for other sharksIf bad players are known as fish, then obviously the good players are the sharks!.