On PokerStars I've noticed a little bit of a trend on the lower limit tables. These limits are just full of regulars with 11/8 stats that are annoying to play against when there are too many on the table. Ideally you want tables with at least two fish that you can exploit. Here's my tip:
Join tables in the five minutes before the half hour or the whole hour.
Why does this work? Well it turns out the people with these stats are grinders. They play a fairly predictable game over a large number of tables. They also tend to play to for a set length of time which incidentally tends to end on the half or whole hour. These are the times when seats might open up on tables with the fish. With so many seats opening up it might even attract a few new fish to your tables.