Here are some basic rules.
1. Use Firefox, I predict eventually chrome will be good, but not yet.
2. 3 add-ons for Firefox, "Better privacy", "Noscript", "ADBLOCK PLUS", adblock is the single greatest thing in the universe and really it alone is a good enough reason to use Firefox over everything else, I personaly have never seen it fail but i can't imagine something this awesome working perfectly so i would say it COMPLETELY REMOVES 99.999% of the ads.
3. p2p downloading, also known as torrents, if you are gunna do it, use the pirate bay and ONLY download torrents with a green or pink skull on them and make sure that the torrent has been up for at LEAST a day. READ THE COMMENTS, ALL OF THEM.
4. Porn. 99% of viruses come from it, why? Because they (the virus writers) KNOW that each and every day at least 1 person will llok for porn on the internet, they are sadly correct. If you really must, use a big and/or popular site. Don't sit down, google search -BLAM- -BLAMING- BLAMS- then click the first link you see.
5. If something pops up asking you to download something just do yourself a favor and hit ctrl+f4, if that don't work open up the task manager (ctrl+alt+delete), right click your browser on the list, go to process, right click the highlighted process, end process. Profit.
6. Anti virus software, if you've heard of the company or the software before, it's probably not that good. If a anti virus is popular enough hackers/virus crafters etc. will make sure their programs can get around it. On the flip side if it's not big enough it will have crappy support and updating. You want the middle of the road, I personaly use webroot, it works although it can be intrusive.
pro tips are pro. Give your own advice and opinions.