The only replay I could find against a half-decent Necron. Half decent in that I screwed up the warrior harass in the game before and ended up without a paddle, so to speak.
Probably not the best replay (on my part or my opponents), but you should be able to see how I try to use my warriors - Firing only as long as I'm taking out the front rank of his (confusingly named) warriors. When the NW (ha! Slightly more sense-making!) start getting most of their folk in range, you run away a little bit further and repeat. Use your speed and your firepower, while trying to keep his out of the picture.
Try and stay out of range of turrets and lp2s, kill whatever scarabs you can and make sure you seize as much of the map as humanly possible.
When you hit T2, get scourges to deal with flayed or destroyers and the Archon for his crucible. When/if wraiths start coming out, try to run around a lp2 or (if possible) throw your warriors into raiders to keep them safe, because wraiths will cause you alot of problems.
I'm sure there's a lot I haven't covered, but I think that's the basics of the plan. Warrior mass and away!
I'll see if I can get in another game or two against some necrons and make sure to save them.