Kick it, and/or then take the nearest cover. The kill radius on a standard US hand grenade is 5m, with the causality radius being 10-15m. If you can't punt it 10 yards on open ground and take cover, you suck.
Just randomly running away from the grenade is a good way to get shot, and any well made position has grenade sumps (holes in the bottom to take the blast and shrapnel, with the floor angled toward them) and if your getting grenades thrown at you, the people who threw them WANT you to run out of your position.
If you're in in an urban area, there's probably somewhere you can kick it and/or hide, even if it's just a little niche, where it won't kill you (you might get hit with some flying metal, murphy's law).
lockeslylcrit said:
It the thrower isn't retarded, he'll cook the grenade beforehand. Thus, the only logical solution is run for cover, preferably a concrete wall.
It's actually a terrible idea to cook grenades.
There's the Gunny to tell you why at around 3:56. [http://www.youtube.com/watch?v=KvNWFTV2OlM]