What are your details?

OS(Win XP etc)
LW & Java version (help > about LW & you'll see)
Firewall you're using
Modem/router brand & model
ISP
Connection type (DSL etc)
Where you connect from (home, school etc)
Are you sharing a connection with other computers
Is this your first try with LW

Try downloading a file from here & see what speeds you get
http://www.magnetmix.com/video.shtml

Also try deleting your LW preferences folder (when LW is closed). Instructions here
Fixes for LimeWire
Deleting this folder will mean that you'll have to set things up again within tools > options. If there are any settings you're not sure of, go through & write them down before you delete the folder