Back when I built my IP-057, here is what I did to dial in my Rockshox Reba RLT Dual Air. I'm sure this method would work with most Rockshox forks so I thought I'd post up as I've heard many people do not take the time to dial in their fork.
1) Air pressure - Using the o-ring, I checked my sag and found that even though the air pressure was right for my weight, there was too much sag so I added some air with my shock pump, matching pressures in both the positive and negative air chambers).
2) Rebound - I set the rebound to about 20% from the fastest setting. Some sections of the trails I ride are pretty fast (20+ mph), there are lots of small rocks and roots on the trails so a faster rebound setting seemed like it should work well.
3) Compression - just a few clicks from fully open. I wanted to use most of the fork travel.
4) Flood gate setting - This is a little tricky and it seems to have more affect than I anticipated, even when the fork is not totally locked out. I set this about 25% from fully open.
The above settings made a very noticeable difference, fork was much smoother and took away much of the harshness I was feeling on the trail. I hope this feedback helps others get their forks setup for a better ride.