Never download more than two files at a time and make sure there are alot of seeders and leechers for the file/s you require. I usually average 70KB/s but as I have a fast internet conection quite alot of files download @ 150KB/s+.
EDIT: When I download I do not surf the net I just leave my computer alone untill the files have downloaded.
Try Utorrent with mininova it's very popular.
ALWAYS scan your downloaded files for any viruses and spyware before you open the file