Another good way to improve ratio is to:
1) Find a new torrent with many files that hasn't been fully seeded yet (i.e., shows only one seeder, but many leechers). This will only happen when a torrent is very new.
2) Download the torrent, but only select some of the files (like the smallest ones) to download–which means marking the other files "don't download" in your torrent client.
3) Let this torrent seed for at least a few hours, preferably a few days.
This way you will get the file(s) you have selected fairly quickly, and then be a resource for the other leechers who are trying to get all of the files. Your ratio on this torrent can easily get to 5:1 or even 10:1. And, this "trick" doesn't damage the system or harm other users.
The only disadvantage here is that this torrent will show up as "seeding" in your torrents listing as long as you don't have all of the files. Once you've reached a good ratio with it, or most other leechers have gone away, just delete the torrent, and keep the files if you wish.

