Just start off increasing your speed slowly until either you reach the speed you are aiming for, your idle temperature gets higher than you would like, or your computer becomes unstable. Once you reach this point, back the speed down a little more to be safe. You can run a utility like Prime95 to test stability. Overclocking WILL shorten the life of your processor, but most people dont plan on keeping it for many years anyway. The only ways to really ruin the processor are by giving it to much voltage and the temp being too high. Search in the CPU forum for the max voltage of your processor, prob around 1.7-1.8v reccomended. As for temps, many people would say different things. I like to keep my idle temps in the low to mid 30s. Most people when overclocking will keep them at least below the mid 40s. In the 50s-60s you are likely running too hot and will experience instability.
As for the HS and fan, depending on your budget, go with an Thermalright SK7, SLK800 or SLK900 depending on your budget. Then pick out the most powerful, loudest fan that you are willing to listen to. Panaflos are the favorites of many. Artic Silver III will also give you a little extra cooling ability.
Brian