Table selection can be very important, but I find at places like Party Poker where there are thousands of players playing at any given time it's not as important as normal.
The players move in and out of games so quickly, that any given table is rarely even comparable to how it was 1/2 hour ago. In these situations I usually just sit at a table with a seat open, wait for the blinds, and then just play. If I notice it's especially tight or something I might change tables, but it's not very often.
On some other sites table selection can be essential to having a good session. Personally I like action tables, but I don't like to see someone with a huge chip lead. I usually don't want more than two people with more than twice the max buy-in, and I like to see a few short stacks because a great number of these guys are just looking to lose the last of their chips so they can quit playing.