Hello everyone!
A few weeks ago, I wrote a short text that is made specifically to guide people who bought a used Mac to clean it, repair it, and make it almost brand new. There could be a few things that are missing or wrong, but here's the text:

A few weeks ago, I wrote a short text that is made specifically to guide people who bought a used Mac to clean it, repair it, and make it almost brand new. There could be a few things that are missing or wrong, but here's the text:
Tell me what you think and what there is to improve if there is anything.WHAT TO DO WHEN I GET A NEW MAC
- If it has an OS installed:
- - Check its specs and determine the model.
- Reset the PRAM and reset the SMC or PMU.
- Determine which OS is the best:
- - Latest IF the CPU clock speed is at least somewhat higher than the required one and the RAM is preferably higher than the minimum.
- - Previous-to-Latest IF the CPU clock speed does not reach the minimum or if the RAM is too low.
- - Never ever install a system OS higher than the official requirement because it'll run like ****.
- (a few examples: iMac G4 1.25GHz w/ 512MB RAM: 10.4 would run best, but 10.5 would work as well, but it is preferable to upgrade the RAM first (see below))
- (iBook G3 Clamshell 300MHz w/ 96MB RAM: Definitely Mac OS 9. 10.2 would "run" on this, but will be really slow, so it is still best to up the RAM)
- (PowerMac G5 2GHz w/768MB RAM: This computer is so powerful there is zero need to run a version older than 10.5. Still, a mem upgrade may be preferable)
- (MacBook Early 2008 2.1GHz w/ 2GB RAM: Considering this is a modern and quite useable computer, 10.7 is the best solution, even though there will be slowdown and lag. Trying to force 10.8 or higher will most likely be a stupid idea, and won't be worth it. 10.6 if performance is more important than compatibility.)
- Install the selected OS.
- - Format the hard drive, verify for problems, and if possible, do a secure erase.
- Go through the entire update process; if available, directly update all software from Apple, if not, download files directly from their website (Combo updates, security updates, Safari updates, iTunes, etc.)
- Customize settings pretty much.
- Install programs such as iLife, iWork/Office, TenFourFox, etc.
- - Latest compatible version is preferable. Even if specs don't really match, it doesn't really matter as they're simple programs.
- Test all components, the keyboard, camera/mic (if applicable), display, backlight, speakers, disc drive, all ports, etc. etc.
- Perform full battery test; charge and discharge the battery multiple times, and determine how long it lasts.
- Consider and perform physical upgrades:
- - If battery is too weak or dead, it is best to buy a new one, if possible.
- - Upgrade the RAM to pretty much the max or near-max possible.
- - In certain conditions, the hard drive may be used or dead and thus might be best to be replaced.
- - - If that happens, you will need to re-do all software-based steps. Restoring from a CCC, SuperDuper, or Time Machine backup can make the process easier.
- - If possible, clean the fans and re-apply thermal paste.
- - Install Airport card if it isn't already.
- - Clean the entire computer overall.
- That's about it. Enjoy.