You can only download as fast as the sources will let you. So if you aren't getting very fast speeds, that's probably as fast as is available from those souces. Otherwise search for more sources. Remember sources include people who are from all different types of connections including dial up. Also, most will be sharing their upload bandwidth amongst many users, so you will only get a share. Also, since much of the downloading happening is via partial file sharing (where people are sharing what they have downloaded at that time but are still themselves downloading the file), so there will be little hops in speed as you download each small packet segment of file. Remember you are downloading from other people, not a website.

Quite a good test is from the magnet site. Try one of their files & see how it goes: + MagnetMix.com +: The Source for Good Content

You didn't mention how fast people are uploading from you at. I find I upload at faster speeds then I download lol