Use AZUREUS.. fuck all the other shitty bittorrent clients!
http://azureus.sourceforge.net/
If you are getting shitty speeds try this program and make sure your HEALTH is showing as green on the far left.. if not you MOST LIKELY need to setup port forwarding on your router.
Without forwarding the bittorrent port you WONT get proper credit for the chunks you upload.. meaning you get shitty speeds.
If you don't know how to setup port forwarding on your router.. you are too dumb for bittorrent.. try Kazaa.
Edit: Just wanted to add that all Bittorrent clients need full access to a port.. not just the one I recommend. Azureus is good because it manages all your torrents in one window and lets you know if you are having connection issues with the health icons.