For Your Info ...
For trouble free computing ... I recommend using these ..
Macaroni ... just set it and forget it. ONLY utility of its kind to work AUTOMATICALLY
http://www.macupdate.com/info.php/id/9633
Macaroni is a tool which handles regular maintenance for Mac OS X's Unix core. Normally these tasks run on a regular schedule, in the middle of the night. However if you don't leave your Mac on all night, they never run. Your Mac won't wake from sleep to handle this. Macaroni solves this problem. If a scheduled maintenance task is not run when it's normally scheduled, Macaroni automatically ensures that it's run at the next opportunity, whenever the Mac is on. Repairs permissions also, on a weekly basis.
Also every month or so ....
Cache Out X
http://www.macupdate.com/info.php/id/9538
Cache Out X clears out the cache entries on your machine, helping you recover valuable disk space on your machine. Items removed include the caches in System, Users, and Library, along with the Internet Explorer download cache. Optionally clears the IE's history cache as well.
Defragging?
From Apple ...
OS 10 Disk Optimization
http://docs.info.apple.com/article.html?artnum=25668
"For most users there is little benefit to defragging ... however ... if your disks are almost full, and you often modify or create large files, there's a chance they could be fragmented. In this case, you might benefit from defragmentation. "
Tech Tool Pro 4 will defrag if you must.
Most importantly ... buy a copy of "Disk Warrior" and run it every couple of months.
Try to also avoid "third party system hacks".
For complete peace of mind, before a year of ownership runs out, get Applecare. It will pay for itself with one service issue.
Good luck and welcome to the Mac World!