If you're not used to eating very hot peppers, use nothing but lombok peppers to make your first sambal. You can always upgrade by adding some rawit or other varieties to a later batch.
There are probably as many sambal recipes as there are Indonesian aunts and grandmothers. This one here is a fairly basic sambal recipe, but not the most basic there is; that would be sambal oelek, which is pretty much ground up lombok peppers and not much else. Boring, right?
So this version uses onions and garlic to add some aroma. And also, the onions help dilute the peppers somewhat, so this sambal is not crazy hot. That makes it suitable for daily use, if you like that kind of thing.
For extra flavour, I've added ginger (djahe); feel free to leave that out if you don't like it. Experiment! Making sambal is easy and fun!
I learned to make this from KKN-Peter at Hack42. Remember kids, brush your teeth, and support your local hackerspace!