I’m always seeing questions like, “How long should I seed after downloading?” Seed until the share ratio is at least 1.0.
For the original BitTorrent client, this means making sure the upload total is equal to or greater than the size of the file or directory.
For apps like Azureus, open the Options, select Queue > Seeding > First Priority, set the any/or option to any, and set the share ratio to 1:1. You may also want to set time since seeding to something like 3 hours, just in case others are looking at that for merit.
If everyone shared to at least 1.0, there would always be a seed. Better yet, by sharing more than 1.0, you help others achieve faster download speeds.
Finally, let’s talk about how much you should share. I’ve had torrents that I’ve had to seed eight times over, just because there aren’t others who share to at least 1.0. Eventually, I just stop the seed; it’s not fair in my opinion.