I'm sure this is a common question. I've had my macbook for a little over a year and use it exclusively for the internet. Recently, I've been using the "force quit" option because the machine freezes and that colored, spinning wheel is on the screen. It has to be because of junk files. Right? How do I clean it up?
How much RAM do you have installed in your MacBook? (If you have less than a couple of gigabytes of RAM, and run a bunch of programs at the same time, this may be the crux of the problem.)
Is this a problem that just recently started, or have you always had a problem with programs freezing that required you to force quit them? (If you have had your computer for over a year, and this has just recently started, I would assume that the problem isn't that you don't know how to quit programs, and i would suspect that you also have a reasonable amount of RAM installed.)
Do all of your programs tend to freeze during use, or does this only occur in specific programs?
Does the problem get better if you only run one program at a time?
I suggest that you run all of the recommended routine maintenance on this Web site,
OS X Maintenance And Troubleshooting
and see if that resolves the problem.
If it does not, try this:
Locate and launch Activity Monitor (in Applications/Utilities), click on the heading for "%CPU" and click on the triangle next to "%CPU" until things are sorted in order from biggest to smallest. See if there is something hogging all of the CPU time.