There is a system cleaner called Onyx, it allows you to clean out temporarily files, etc, and verify your hard disk. In my experience it does a better job than Clean My Mac (or whatever it's called). For the most part I do not believe you need anti-virus software, and whenever I took my old Pro in for maintenance, the tech guys always said that the anti-virus programs would slow my computer's performance (which they did), and were unnecessary.
Using a web browser that has an ad blocker is very important as well. I used Firefox (involved downloading the Ad Blocker add-on) but I believe Chrome has a great ad blocker as well. Then you can add websites that you want pop-ups from (say for yahoo mock drafts). A little message will appear in the top right hand corner of your Firefox window and you can choose to add that site (Yahoo fantasy mock draft, etc) as safe to allow the pop-up. This is very important for streaming shows or games because you do not see those pesky side advertisements, no banner advertisements and do not get any pop-ups. Makes a huge difference. I did not see a single advertisement on my computer until my Pro broke down after 5 years. Now I see them frequently on my iPad and it is very annoying.
Hope that helps!
Cheers,
Ross