This free utility from MicroMat--makers of TechTool Pro--does a very good job of helping you reset your PRAM. It even offers you a way to save your previous PRAM settings if you ever want to revert.
Resetting NVRAM
Resetting the NVRAM will resolve many issues. If done correctly, it should not damage any aspect of your computer.
Two ways to reset Macintosh NVRAM
1) Holding down the following keys as the system is booting:
[Command] [Option] n v
2) Via Open Firmware - does not reset PRAM, according to Apple. To do so:
Hold down the following keys as the system is booting:
[Command] [Option] o f
You will be presented with a gray screen with a command prompt.
Enter the following Open Firmware commands, followed by [Return], in order: