Ok this is going to be a long one...
"DISCLAIMER" I am NOT responsible for any illegal downloading software aka pirated stuff... That's all let's get serious.
1. check the health of your torrent. If there are like 2 seeders and 20 leechers that is not a good torrent.
2. Check if your ports are open choose anything higher than 6881. I have chosen port number 7000.
3. To open a port:
a. go to system preferences
b. go into the sharing icon
c. click on firewall
d. click new type in any name and put the port that you want to open on BOTH boxes.
4. Go to
http://www.canyouseeme.org/ to check if that port is really open.
5. If it is open then go to preferences in transmission and click on network and type in the port number that you chose
6. Start downloading!
THINGS TO REMEMBER:
Torrent clients have a built in credit system, for example if you download 1 gig then you must upload 1 gig, this is the share ratio. The best ratio I think is 1.00 or 1.25 It might take a little while to start up but then you will get faster and faster! Of course this all depends on the share ratio and the health of the torrent. As for seeders I don't think that there is a way to fix that if the torrent is popular chances are that there are going to be a lot of seeders, if not then not many seeders.
That's it! If you have more questions then just post them