Well in a sense there's no such thing as a safe overclocking, but it can easily be done without any damage to components.
You should make sure that you have sufficient cooling equipment and then there are few methods for it. Firstly you may have an overclocking porgram so you can do it through windows, but it's not as good as overclocking through manually modifying BIOS parameters. I haven't overclocked mine too much, and cannot remember good guidelines for relatively safe overclocking regarding increase of frequency and voltages. You might find plenty of information regarding it from dedicated sites.