for the very first: your download speed has no influence to your ping. only the connection technology has influence: for isdn it is normal to have about 80-100ping, for adsl - about 60-80, for t1/t2 - about 10-20.
the main rules:
1) exit all programs/downloaders that eats your connection bandwith: torrents/skype and such.
2) play in servers that are near your location/country.
3) there u will find nice trick to lower your ping: http://www.ilterendiguild.com/v2/showthread.php?t=1889
it worked for me as well: i lowered ping from 60-80 to 20-30.