First of all, i'm french... so sorry for my bad english...

Well,

When you are in low sec belts, some rats are camping (or will soon spawn...).
There is 2 differents cases:
Sometimes there is some battleships, with big bounty, you can shot'em all.
But when there is only frigates(or poor ships) with no real good bounty prices, shot them all, except a frigate (the little one...).
Then, leave the belt, (go to an other and make the same trick) The last frigate will call its friends, and its friends could be better (ex: frigates with 1K bounty price could call 10K-bounty-price-cruiser, wich could call some 100K-bounty-price battlecruiser, etc... ) when you think it's enough, shoot them all!


With my corp, we turn around all belts in a system and improve all bounties, at the end of the rats session, we kill all rats and go back station full of ISK. We can make about 10M isk profit per hour in big systems...

Note: make sure that there is no f*** noob in the system wich can kill your pops (pops: spawn of better ships with better bounty prices...)
Note 2: this trick is easier with a fleet of 3 persons: One for tanking, an other for DPS and the last on for salvaging (a scoot could be interesting too, but that's isn't easy to gain isk with some hostiles around...)