What three things...

So I'm making the big move after a long, long time from Chaos over to an army I've never seen played in person. So, what would you say, going from a Nurgle heavy army to DE, are the 3 biggest things I need to keep in mind?

Heres my proposed army list, for reference (with a few alterations a few posts down).

http://www.thedarkcity.net/t8520-1750pt-first-de-list-ever

Hey there, glad my first post here can be dispensing some friendly, if general, advice. If you want I can give more specific advice based on your list but I feel most DE armies need to consider the same basic things!

#1: Cover. Remember carefully hiding your plague marines (I'm boldly assuming you didn't run csm with marks) whenever low AP weapons were about? Yeah, do that all the time now! One you're out of your transport you need to put stuff between you and your opponent so he doesn't gun you down. This includes LoS blocking terrain for our vehicles. Speaking of vehicles...

#2: Flying coffins. I love DE vehicles, always have! They're one of the reasons I first picked the army up all those years ago. That said staying in them is basically a death sentence för your troops. Your vehicles will be very fast which can lead you to inadvertently position them in very bad spots, so knowing where your firepower needs to be and when to disembark your troops is essential.

#3: Secondary Objectives. Dark Eldar are much better at claiming secondaries than primaries, at least in my experience. Your mobility will allow you to easily claim linebreaker, your guns will easily secure first blood and your archon is killy enough to murder most any warlord in a fair fight (which you will never, ever give it). Your mobility also ensures that you will be able to deny your opponent objectives by driving up to him in the last turns and contesting. This of course doesn't mean that you shouldn't go for primaries if you can, but remember that sometimes you gain more from crippling your opponents scoring.

Agree on all fronts, I suppose my number one rule would be an extension of what was touched on before.....

Do not fight fair - not even slightly fair. And not ever. Use your entire army to obliterate specific targets at the right time. I find getting into the characterful mindset helps with this. Your army should always act like a precision instrument, wield it like a scalpel. If you're cutting in multiple places at once then make sure you know exactly why you are and that there is some goal beyond simply 'causing damage'. Stack every engagement as much in your favour as possible without needlessly over committing - have exactly what you need in place to do the job

Know your opponents target priority and 'game' it so their killing things you want them to kill, or at least not killing things you need them not to kill. Know which of your forces are sacrificial and where their sacrifice will occur.

Remember your speed. Don't like how a flights shaping up, don't be in it. Redeploy and stab him in the kidneys instead. Be willing to let something dangerous live if it gets you a chance to cripple him in the long run, but make sure you have plans to mitigate the danger.

Coming from Nurgle CSM to DE what are the main differences?
Hurm...

1. Our Troop slots are a gift, not a punishment. Bring many Troops, not a few.

2. 10 Plaguies are twice as hard to kill as 5 of them. This is theoretically true with DE as well, the catch is that most units will overkill 5 and easily kill 10. Bigger is not always better with us. More target saturation, though, is better. As a connection to this, get mentally away from the idea of objective sitters. We don't sit. When we sit we die.

3. Speed. We have it, Nurgle doesn't. You no longer need to start the game thinking about how you'll be getting Unit A to Objective B. Frankly it likely won't help you if you do because Unit A might be dead in a flash at any point. However, you ill find our ability to move from almost anywhere to an Objective is really good, start thinking about objectives Turn 3, not before. Before that focus on killing and hurting your opponent as much as possible - tabling is an objective claim all its own, and we are well capable of near tabling an opponent in 3 turns because we really shorten the amount of time to get into the fight.