I did it first time last year.
The qualifier is the key part to get right.
Your race number defines where you start in your group of 200.
So if you're say 923, then you start 123 people back from the front of the grid (well it's done in lines, but you get the idea).
The only points to pass people are on the fire road or the wide 'moonscape' - a couple of people let me past on the singletrack, but I found I did get held up by other riders.
I managed to make up about 50 places based upon my start position.
Odd as it may sound - practice walking some of the more technical sections - there was one section last year which quite a number of people walked (it was perfectly ridable) - once one person was off & walking pretty much everyone else had to follow suit (this happened on my quali, so I was forced to walk)
Qualifier decides which main race you go off in, if you qualify: -
1-35 = Megavalanche
35-70 = Mega Challengers
70-105 = Mega Amateurs
After that it's the Mega Affinity 1 & 2 (but you don't get the mass start in these groups).
I made the Mega Amateurs, but was towards the start of the grid (this turned out to be good luck). I got a much cleaner run down than one of my mates who qualified better than me & made the challengers race at the back of the grid.
Ideally the best places to be (if you're not Dan Atherton etc.) are at the front of the challengers race or the front of the amateurs race.
Don't be tempted to take a DH rig - 160mm travel full suspension is most suitable. Quite a number of people were pushing DH rigs uphill on the fireroad sections, which is when I passed them.