My first year, we DNF'd when we burnt out the clutch trying to get un-stuck on Sandtrap, so I guess my main advice would be not to do that.
Try to carry speed to get through the loose stuff, especially on the uphills.
Oh... and since this is your first rally as a co-driver, pick up some large ziploc freezer bags and tuck one away somewhere you can reach while you're belted in. Your stomach might be like a rock, but you won't really know for sure until you've tried a few stages. But better to have them and not need them than to need them and not have them, right?
Seriously, though, don't worry about things too much - I'm sure you'll do fine.