step-by-step of what Dark Shroud said...
1) Open BitComet. Go to the "Options" tab on the top of the BitComet window and go to preferences
2) Check if your upload and download limits are on "No Limits". If they are, continue to next step, if not then change them to "No Limit" and continue
3) Go to www.speedtest.net (Its an online site that determines the speed of your connection)
4) When it shows you your speed, divide the download speed by 8 to find out your max download speed. Then, again, go to "Options" in BitComet and set your upload limit to 85% of your max download speed...
Hope that helps candy11 :)