on raspberry pi, is so crazy easy. go to console. then type

sudo raspi-config

choose option 7 - overclock. Set it to whatever you want.

All of the settings are pre-approved settings that should run stable without melting anything. The main thing that people report is faster memory card corruption with the higher speeds (I haven't had any trouble and I have been running mine on full overclock for 6+ months)

Check this thread as it might help with a decision:

http://pimame.org/forum/discussion/1074/overclocking#Item_4

I agree I think the Pi is made to run "as-is" without issues with overclocking especially if they are willing to allow it without voiding the warranty. If it dies a few months out of warranty (1 year?) then they hit the nail on the head of good marketing.

I was running overclocked with a heatsink/fan combo at around 38-39C. If I throw it inside a case without heatsinks at the same overclock I leveled off around 64-65C. Big difference in temps but well within the parameters. With that though if I can make it run 18 or 20C cooler count me in.

I think a CPU's biggest threat is heat and over time you start to see some degradation by which I mean things like failing stress tests or your computer runs slower, restarts, randomly turns off, etc. I think overclocking expedites the life of the CPU. Even if it does last a good long time I think it does shorten the life to some extent.

That being said some of the cooling solutions cost almost as much as the Pi or there are some very reasonably priced ones that might extend the life of the Pi. Maybe not. It's really hard to say.

I would say if you enjoy it or feel more comfortable running cooler go for it. I think the heatsinks add a bit of flare to the aesthetics and I like it. It's a hobby and anything goes! I know mholgatem doesn't care for heatsinks on the Pi but I do lean toward them. I do respect his opinion though and he REALLY knows his stuff! ;)