Maybe try a Router re-start (unplug for 1-3 min), for me it helped when my connection lags.
As long as you're online, u-torrent running and the file is not altered/moved from the folder, you seed. When you quit connection, close u-torrent or alter the file(move/delete) than you're not seeding any longer.
BTW. have set your Torrent straight? Not just installing and good. You need to make further bandwidth-tests (at least 2) of your connection to set your Speed in your torrent application straight.
As for the specs in your Torrent and connection, don't be a fool and take a higher number, awerage and good means here, if my load is 16,3 I'll take 16 not 17.
The u-Torrent inbuild test Tool for me never worked, I made them separately to get my awerage bandwidth data.
If you set your Torrent in options straight and it's still laggy, then it's not your fault, your connection or less Seeders.
How it works, go to U-torrent site and use FAQ/Forums there, it's too complicated. I have a manual in german and can hardly understand what they are talking about.
You need your specs in kbit/s!!!
Download-Speed: [++] 262.144 kbit/s (32.768 kByte/s)
Upload-Speed: [++] 163 kbit/s (20 kByte/s)
lil Maths in the Morning, take your Upload speed and divide by 8, multiply the summ you get with 0,8
163/8=20,375
20,375x0,8=16,3
16,3 (my needed max upload rate)
16 is my specific "max upload rate", with a 2000 T-DSL( with from time to time speed if I would have 6000, but very close), if connection is still laggy you may give it 1-3 kbs less in max upload rate, try if that works, than it should be faster. Bit torrents do upload always with your max. upload speed, that's why it is important to set it according your specs. To avoid an overkill in your connection, which will show up, that it laggs.
As I said I can hardly understand this, but it works, from time to time I check my connection and apply changes if there is a need.
This should help some of you experiencing lags.
Regards Knochenlutscher