Newbie to Mac - which must-have apps do I need?

From what I hear do not put MacKeeper on your new box.

You do not need (or want, trust me) any antivirus or "cleaning" apps. For web browser, Safari is great, although you might try Google Chrome. iPhoto is all you really need for photos. If you want a game or two, some of my top favorites are Angry Birds, Asphalt 6, Plants vs. Zombies, and Bejeweled 3. But honestly, you have everything you need and want already on your Mac ;)

There are no must-have apps. There are some must-not-have apps, such as "haxies," “add-ons,” “toolbars,” “enhancers," “optimizers,” “accelerators,” “extenders,” “cache cleaners,” “defragmenters,” “firewalls,” “guardians,” “defenders,” “protectors,” most “plugins,” commercial "virus scanners,” or "utilities." With very few exceptions, this kind of software is useless, or worse than useless. MacKeeper is a prime example. The more actively promoted the product, the more likely it is to be junk.

The only software you should install is that which (a) directly enables you to do the things you use a computer for: creating and editing documents, communicating, playing, and so on; and (b) does not modify the way other software works. Never install third-party software of any kind unless you know how to uninstall it.

Start learning about the platform here:

Apple - Support - Mac 101

...how (or should I) manually keep it cleaned up?

Don't.

...unwanted cookies, history, etc.

Those can be removed from within Safari.

Cassandra --

You'll find that Macs are very self-sufficient. Unless you regularly visit p*rn sites, or use Torrents, there's nothing else you really need to worry about. If you do lots of video or sound editing, you might need more RAM, and back up those files to an External HD for safe keeping.

Welcome to the club.

Glad you've made it!

Browsers should set their own history number of days and quota for size, but they don't , and they can get 'carried away' with web caches, temp files, history. Safari even takes bookmarks and 'caches' it into individual files (so that Spotlight can find bookmarksj!)

So yes I do. I don't like having to do so manually and think there are better ways.

Chrome has and can get huge caches. Safari as well. Mozilla has "auto" and seems to try or you can manually set it to what you want.

Any of the "cache" cleaners can be abused or over-used.

I also like to "intelligently" remove ad-cookies and those that are not needed by me for web sites and that is another vote for using one and no OS X isn't smart enough to be totally self-sufficient.

And all of that will fragment free space. Mac only deals with large files and works pretty well as long as there is "enough" free space to not be an issue. But then I find even cloning the system to a new drive - which also skips copyiing temp files and consolidates free space, works great and I do it regularly (the old drive becomes backup and use the clone as new boot drive).