First and The Most effective way to increase speed is using Vuze instead of any other torrent client.
Other Ways:-
There are some Setting in torrent Client that you need to change to Increase your download Speed. Some of the setting(with value) are listed below.

• Torrent Download and upload Speed:-
  
  1. Go to Options > Preferences in your utorrent Client.
  2. Click Bandwidth option as shown below.
     
  3. Here put zero for both max. upload rate and max. download rate.

• Port:-
  
  1. Go to connection option from the same window as shown above.
     
  2. Press random Port option as shown above to change your port.
     Note:-The concept behind changing port is that sometimes your isp may block your torrent ports(active torrents port) so it is good to change your port at regular interval.