If you have a router, and can access it (by typing in your IP into Internet Explorer and log into the admin account), go to PortForward.com - Free Help Setting up Your Router or Firewall
and select your router. Then application, and follow the instructions given.
One thing that can help is doing a speed test. Make sure there is no internet use at all (except you, obviously, but make sure you only have one window/tab open) when you do this. Go to Speakeasy - Speed Test
and select the location closest to you. Post the results here.
You'll want to cap your upload, but i can't remember exactly how to find out your optimal number. I have my upload capped in Azureus at 1/10th my upload speed. Also, you'll want to limit the number of maximum torrents you can have going at once. Generally, this number is 3. If you have too many torrents going, your download speeds will be affected.