Some thoughts. Nothing is going to protect you 100%, see below.
I just ran some antivirus scans on a infected computer for a friend.
1. Malwarebytes = nothing found
2. Eset online scan = cleaned a bunch of junk
3. Malwarebytes again = Found 2 things now
4. Super Antispyware = more nasties
5. Trend Micro housecall = more nasties
6. Microsoft Security essentials = found one more trojan (fake AV)
7. At this point I suggested a backup of data and a full reload.
I only list the above to show why being cautious is needed.
I would add Web of Trust to your listhttp://www.mywot.com/
It isn't always accurate but in conjunction with common sense while searching it can help.
I stay away from yellow, red and unrated sites.
I run Norton Antivirus with Antispyware, WOT, Firefox with the NoScript Add On http://noscript.net/
Other things you can do include a host file that will block known malicious websites.
Use the challenge / response system for email attachments.
Only install things you need.
Do not click anywhere on a popup. A malicious popup offering a free security scan for example can take a click anywhere as OK including a cancel button or the red X in the corner. If that happens just close the browser and reboot.
Good Luck and enjoy the computer