If your going to be overclocking, then get water cooling if you can afford it.
But for less extreme overclocking, just a good air cooling system will work. Just throw in more case fans and upgrade your standard cpu heatsink for a more powerful one.
Also some of the downsides of overclocking are that it generates a lot of heat that can damage components if not cooled properly. Also some people say that overclocking can reduce the lifespan of some core parts.
CompTIA A+, CompTIA Network+, Cisco CCENT, Cisco CCNA Routing & Switching