If you have a cable modem go to Pc Pitstop(if you dial-up it's still a good site.) You can test your dl/ul speed, run some diagnostics,check ping times,
and a bunch of other stuff also.
After you run the speed test. Download the Cable modem DSL Auto Fix,it
modifies your recive buffer size mine is set at 64240 bytes and this should give you a big speed boost.
I went from around 1882 kb/s to 3000 to 4000.
after I used the auto fix.(you can do it manualy to,thru your registry but be careful.)
Also If you have a cable modem unplug it from the back(usb or,ethernet,and power) every once in awhile if your dl speeds seem to drag.
Leave it off for a few minutes.
It recycles your modem and your dl speeds should pick back up.
Hope I have been some help.