I've looked into just about everything on Necron tactics. I have read other people's ideas and battle strategies. Through this I have come to one conclusion. Most people are wrong. A large majority of people who think they are helping necron players with their advice are actually doing the opposite. That said I'll give a brief description of what I think is ideal in a necron army compared to the tips others give.
1. One of the main tactics I found for necron army builds is taking tons of warriors. Ok, warriors are good but you shouldn't take 5 units at full capacity. during my last game against Agni Prime my warriors were practically useless. one thing I know for certain is, keep the numbers LOW in your units of warriors. 10 is perfect but 11 to 13 warriors are ok too. In a 2000 point game you should take 4 squads of this small size. Especially in a capture and control mission, you need lots of troops units. Even if you can zoom in with your destroyers to contest, to win you need to have some points under your control.
2. Tip number two, TAKE HEAVY DESTROYERS
I've read so many negative comments on heavy destroyers, about how they are worthless. As far as I can tell these comments are wrong. especially in our gaming club armor is power and saves keep your units alive. high toughness is great but a good armor save is even better, most players know this and use it in their armies. you need a way to get past that armor. Heavy destroyers do that, and in a pinch you can run them in to contest a point. One squad will do just fine, try and protect them though. Destroyers and heavy destroyers are tough but not invincible.
3. My final tip goes for everyone non-necron players included
Don't put too much faith into any one unit. Trying to run a list based solely around an amazing super unit is a losing tactic. At best you will end up killing of one or two units with your unit. when other players see a unit like that they will light it up. If your not trying to be sneaky or you think your "super" unit can take the fire of a whole army you will be sorely disappointed. I've tried using my destroyer lord in this way and he kills things but he ends up dying too quickly. play defensively, play smart, and don't think that any one unit will win you the game. Winning will always be a matter of making the right choices. Starting with what units you take and ending with the final culmination of the game. The winner will be determined by who kept their cool and made the best choices and who took the safest risks.
hopefully I haven't ranted too much and good luck to all players in the upcoming 40k day.