I've already answered that in part 1. While that post was more about why I believe that competitive play isn't dead in the new edition of warhammer 40k. This one is more about how I believe it has changed, right at it's roots.
We all remember the nature of competitive play in previous editions of the game. Who didn't try their hand at competitive list building or using Internet tactics? I certainly did. And I only really play for fun! My point is that these things have taken a back seat in the new edition. You simply can't build a list to cope with a large portion of situations that can arise in a game. As for tactics, if you stick too religiously to Internet ones, you will be punished. You have to, more than ever, be able to adapt to the changing situations. With ever more left to chance now, the situation can change in a mere handful of dice rolls. With overwatch and psychic powers, a lot more of the game is now based on dice rolls. Your prized unit could become red mist in a hail of BS 1 shots, or your opponents expensive pysker could roll crummy powers, then blow himself up. And with even more options in the new codices, along with allies and fortifications, there are too many possibilities to cover.
This is where it has changed: you CANNOT win any game before it starts. Deployment is, as ever, vital, but after that comes the change. Pick each of your units, assign them a role, and stick to it.
I'll take my Khorne army as an example. The general idea was to rush my opponent with as many combat units as possible. It would take extreme discipline and vision to plan in the long run to win against multiple turn 2/3 threats. I then had a few small units of cultists to capture objectives. I would send my berserkers in rhinos to kill off troops such as guardsmen, scouts and guardians. My Maulerfiend rushed at the closest tank, to wreck it quickly. My terminators went for heavy infantry and light tanks. My possessed then ran interference, trying to hold up a unit until the berserkers and terminators finished their job.
The reason this worked, was that my plan would guarantee victory if all parts preformed, BUT, some were given easy jobs, so they could still make a difference when they helped those who had tougher jobs. It didn't always win, but it did pretty well.
That's the point, make a plan, with a doable job for each unit, and you'll do well. Fail to stick to the plan, and its over. But you must be willing to adapt. If your berserkers struggle, but the possessed are holding their own, send the termies to help the berserkers, not the possessed (just an example!).
Key to all of this is playing to your unit's strengths: don't send berserkers against MEQs, unless you outnumber them by a lot. Don't send your maulerfiend against a blob unit. It's common sense!
And play the odds! Remember that Dark Angels player I mentioned in the last post? He took down aircraft in a way I hadn't seen before (its more common now): he pushed bikes behind it and fired a lot of twin linked bolters at the rear armour (10 on most!). It works, and it removes threats without a need for an AA unit.
Just to round up, have a plan, stick to it, assign targets to your units, play to their strengths, be willing to adapt, and play to the odds! It's not too hard!!