1. Remove 'Bandwidth Sucking" Applications
Many applications such as anything related to file sharing (KAZAA, eDonkey,etc)and even some things like AIM are filled with addons that will run in the background while sucking up the bandwidth. This then slows your connection.
2. Install Zone Alarm or some firewall on every PC in your house
First rule is not to just apply these things to one PC on your Internet connection. Make changes to all computers since all you need is one bad apple. I recommend ZoneAlarm which you can get at any computer store.
3. Avoid opening unknown attachments
Many spyware problems arise when people click on an attachment. My rule? If I cannot identify the sender, I delete it without opening. Maybe you should too!
4. Avoid Programs that speed up downloads or browsing
There are many programs that claim to speed up your connection such as Netsonic and GO!Zilla. But let's think about this. These programs download a ton of pages so that when you go to the website again it loads faster. Ok maybe so but what if they update that website? Now you have to again update the local pages so you are really not saving anything. Maybe good on sites that never change but where are these?
5. Change your browser start page to NOTHING
Many times people sit and wait for their browser to open since they have a favorite site setup. Best thing it to remove this unless you want to always go there. This is easily done under Tools-->Options in either Internet Explorer or Mozilla Firefox.