The trick is to drive within your ability. If you don't know a section of the track it's madness to go all in and think you're gonna make it. It's better to go 90% or 80% , and gradually increase the pace as you get to know the track better.
It's also a good thing to do when racing online, or in rain. It's madness to go three cars wide through the Swedencross at full speed, the risk is much too high that that you'll spin off and lose 10 seconds. Calculate your risks and back off a bit instead, that way you'll lose about half a second, but you're sure to make it through.
Some number crunching:
Say that a track has 10 corners. If you go full speed through you have 50% risk of spinning out in each of the corners. Spinning out costs you an average of ten seconds. We can assume that you will spin out in 5 of the corners, costing you 50 seconds per lap.
If you back off and drive well within the marigins, you have 10% risk of spinning out in each corner. But you will also lose two seconds in each corner because you don't go full speed through. That way we can assume that you will lose 20 seconds for the lower speed and 10 seconds for a spin in one of the corners, in which case you lose 30 seconds per lap.
Conclusion: Drive within your limits and play it safe. From my experience, it's the fast laps who wins online at the ring, but it's the safe and clean laps that grabs the silver.
(Also think about this when selecting car. Pick a car that you can drive, rather than a fast car that you can't. And if you still pick a car that you can't drive, play it safe and get to know the car before you floor it)
I think the biggest problem with the nurb is when you're racing people, a lot of them will try to overtake you at place you simply can't without pushing the other car into the grass.
For me the hardest skill to gain on the nurb is the ability to pass people cleanly. If you can master that you're a true nurb racer.
You can approach these situations in either one of these ways:
1. You want to have a good lap
2. You want to make a statement
If it's 1, then again, it's about calculating the risks. There's always two cars involved in overtaking, and if you feel that the car behind you is risking too much in attempting to overtake, then step aside and let him through. If you want to have a fast lap, then the risk of not letting the other car pass is too high because you might get pushed off the road and there goes your lap. Also, if the car behind you actually is that much faster than you on the track, then there is no reason for you to obstruct him, because sooner or later he will make a pass anyway. Be a gentleman and give room.
If it's 2, on the other hand, and you want to make a statement out if it, then simply let the other car take the two of you out on the grass for a little pic-nic together.
About passing cleanly, you said it already, but it's about knowing where is a good place to make a pass, and plan your driving well ahead. There's a lot of tricks, you can for instance stress the other driver to make mistakes, you can trick him to cover up the inside when in fact you want to pass on the outside, and so on. Be creative! A single great overtake on the ring can feel more as a victory than finishing 1st
