the best overclock is an overclock from your BIOS.
This is a small, basic guide with info on how to overclock your system. Personally, I read quite a lot of different guides before I started, just to minimize the chance of anything going wrong.
If you want to know more, searches like 'overclocking/overclocking guide' etc on google may have some interesting results. If you have any questions, don't hesitate to ask!
The link:
http://www.neoseeker.com/Articles/Hardware/Guides/OCguide/1.html
Edit:
I'm sorry. You said in your start post that you didn't want to try anything manually. I believe that doing it manually is not very high risk, if you just take small steps in upping the FSB, and you need to know what you're doing. You need to test if the system is stable at a certain speed.
Also, could you please state if you want to overclock your GPU or your CPU? The thing I described above is for the CPU(the nvidia ntune is for both). Overclocking the GPU goes differently. I'm not sure about the ntune program. But I think it's a good start, if you also take small steps and test your card after every few mhz you overclock.
Hope I still helped you with this.
~Exonimus