Mid-2012 MBP lagging with constant colour wheeling at everything. How do I fix it to run quickly/smoothly again?

Question

I only just got my Mid-2012 13-inch MBP last November, switching over after a long time with PCs. I wasn't expecting any problems with my MBP, as everyone else I know who has one hasn't had any issues. I love it but a couple of days ago, it's become relatively slower than its usual pace. I'm not quite sure what's going on, but as it's still relatively new, it shouldn't be lagging every five seconds with opening an application or switching tabs or typing in Word. I don't do much with my MBP except for surfing the web (Facebooking, etc.), doing homework, and YouTubing. Gifs won't even load properly at the moment. it's becoming frustrating because it's the same problems I faced with PCs that I wasn't expecting from Macs. The colour wheel of doom keeps spinning on my screen and I just want to be able to do whatever to make it all run smoothly and quickly again as it was. (In typing this message alone, the colour wheel popped up and everything lagged considerably for a good minute or so quite a few times.)
Here's some of the info/specs I got from the About My Mac:
Processor  2.5 GHz Intel Core i5
Memory  4 GB 1600 MHz DDR3
Graphics  Intel HD Graphics 4000 512 MB
Software  OS X 10.8.3 (12D78)
I also have 395.89 GB free out of 499.25 GB, and I've also referred to the Activity Monitor with nothing in particular that really uses a lot of CPU or anything like that. I'm also not sure whether or not to do that Disk Utility thing to repair permissions or whatever it is or if I need to test anything in safe mode.
Anyhow, thanks so much in advance to anyone who can help me out with this! I really appreciate it

Answer 1

but a couple of days ago, it's become relatively slower than its usual pace.
Is there anything significant that occured just before the slowdown issues occured?
Your machine comes with a boot hard drive, which is subjective to shock if the computer is moved while the computer is turned on. This has a effect of damaging data on the platters where information can't be easily read or sometimes not at all.
The spinning wheel is indicative of the software waiting for something from the hardware or network, but your using programs that have no use online, so it suggests something is wrong with your boot hard drive.
If the hard drive has difficulty reading data, there is a mechanism in place to try to read the damaged sectors and move the information to another sectors on the drive, since this takes time you get the spinning beach ball waiting.
Another possiblity is you might have installed some sort of very restrictive third party anti-virus that has a background check process on everything your doing. For Mac's this is unnecessary as Apple has included their own and the free ClamXav is all you need to run once in awhile to clean/flag Windows files  which their malware doesn't affect a Mac.
Use the developers uninstaller to remove it and reboot.
it's becoming frustrating because it's the same problems I faced with PCs
Given your age and that you had this problem with PC's, I suspect your very harsh on your machines or haven't been educated about how fragile they are and can't be moved while operating.
To solve your issue my suggestion is to first make a backup of just your users data to a external drive, also to another drive using TimeMachine which will make a copy of your entire system.
So this way you have at least two copies of your data off the machine, the TimeMachine might fail to restore if it backs up corrupted data. Thus the extra copy of your personal files on another storage drive once the fresh opertaing system and programs are reinstalled.
Most commonly used backup methods
Next take the machine to the Apple Store and tell them your seeing beachballs on everything your doing. They will replace the hard drive under warranty, ask if you made a backup or not and of course tell them you did with TimeMachine but don't think it's going to reliable because of the issues on the boot drive, tell them  you have a extra copy of your files on a another storage drive.
Ask them to help you reinstall OS X and Apple programs for you if they can, then all you have to do when you get home is to copy your files from the storage drive. This would ensure any corruption of OS X or programs is eliminated.
I would buy AppleCare if you haven't done so already, but just remember, warranty/AppleCare only covers factory defects, not user inflicted damage.
However there is some times where hard drives will fail on their own accord in a few months after purchase, which might be the problem in your case as there is a sudden motion detector and it's supposed to freeze the hard drive to prevent damage to the platters.
Good Luck