Make sure you do not have any programs running automatic updates in the background e.g. for windows, antivirus etc
I take it you are directly connected to a router and not using wi-fi ? Wi-FI is really poor. Are you in a single property or a block of flats with a communal phone line? More users are worse
If you are in a single user house then there is not much you can do about your ping apart from contact your isp provider.
To check where the problem lies use pingplotter http://www.pingplotter.com/freeware.html
This shows you all the hops or connections.
It should slowly increase but if one server is the cause then that will show up as a large jump.
Your isp can only take action if the large jump is the first connection to your network, this is called the BAM server
If your largest numbers are here then contact your ISP provider with the evidence
IF your are through a telephone network
you could try this
http://www.shop.bt.com/products/bt-iplate---bt-broadband-accelerator-58LT.html
If you phone your ISP helpdesk;
1) He will probably tell you to power off your modem fully and reconnect, your modem will search for the lowest BAM, this might help
2) He will ask how many users are on line in your house and ask you to make sure they are not connected
3) He will also ask how many phone connections you have, do you have splittters installed,do you have your filters installed correctly,he may get you to try taking all other phones out and connecting to main socket
IF you are from UK he may blame BT and their network and ask you to get in touch with them to check your connection between house and exchange
you may want to try steps 1) 2) and 3) above and get figures for each off pingplotter before phoning- the more evidence you have pointing to your isp the better
If you are on cable then its down to your ISP
hope this helps