If you are using wifi try a direct connection to the modem to make sure it isn't a problem with your router if you have one.
I have a desktop so it's a pretty big difference when working with a laptop. But I had a problem from going to 30 - 500 latency overnight! I found out that when I directly connect my modem it was 19-20, which is very close to the 20-30 I was getting wirelessly. Come to find out my VGA cord was rubbing against my wireless antenna behind my computer! Everything is back to normal now.
All-in-all, I would suggest first making sure your routers ports are opened for whatever you are trying to do. Then make sure your wireless routers is centralized in your house away from ANY and I mean ANY! metal. I had a little fold chair next to my wireless receiver and it was interfereing... Then of course make sure your fire wall is set up to allow any connections. But it rarely ever has anything to do with the latency. After that go to your technical support trouble shooting for networking.