To set up ratios for public trackers we recommend you set ratios to 2:1 here is how you do this

Go to settings in your rutorrent interface

Select Ratio Groups

by the side of ratio 1 set min and max % to 250 as shown

When you download from public trackers right click on the torrent and scroll down to set ratio group

and select the one we just set ratio 1

This will now stop seeding when it reaches a ratio of 2:1