Your question may have to be a little more detailed. I have A LOT of thoughts on poker tactics, as im sure everyone here does.

I did a little online multi table experiment myself, I didnt put 100% effort into it, and my outcome may be a little biased because i came out a loser. Either way, what it all seems to boil down to figuring out your objective and then game and table selection.

At first I decided that I wanted to experiment playing strictly the odds, only calling when I was getting the best of it post flop, meaning mostly draws. I was playing anything twogapper suited, any connectors and any Ax Kx suited. I found this only works in really small limit games, because your opponents have to be playing extremely loose. The amount of money that you give up by folding hands that could win with just top pair is too great to be playing in any meanigful game. If you dont mind making 3$ and hour by playing 9 tables at a time, give this a shot.

Then I tried playing position tactics, and this becomes difficult when multi tabling because this strategy is very dependent on knowing your opponents. Your not going to blow a maniac off a hand even if you have the puck on him all day, and accordingly your not going to get enough good hands in position to isolate the maniac unless your playing in a big and/or tough game, and again I wouldnt want to multi table those kind of games. This experiment cost me a pretty penny.

Premium hands is probably the most profitable way to multitable, although even in a decent sized game its hard to grind out any significant money even when playing 3-4 tables at a time. This is because of reverse implied odds. Its so hard to figure out where your at when your playing premium hands only and the flop comes down all paint cards. Your edge is so small, that anything your gaining you will be giving up by not being able to play position and knowing your opponents. I THINK one could break about even or on the plus side playing this way at 4 tables, but my personal result came out negative.

I would suggest 3 tables max to start. If you find you cant focus on your opponents, or tilt easy then drop down to two tables. Nobody can really answer this question for you, its a matter of preference and ability. The better your focus, the more tables you can play.

Hope this helps.