The place where DIYers get most hung up when it comes to changing spark plugs is knowing which spark plugs are right for their vehicle. The short answer (as is often the case) is: stick with the plugs recommended in the owner's manual. The manufacturer knows exactly what each engine needs, and the intended spark plugs will meet those needs precisely.
You may have heard that going one step "hotter" or "cooler" on spark plugs will have some performance or efficiency advantage. While that is sometimes the case in certain modified engines, it's generally best to opt for factory-specified plugs.