I bought a special tray for chips/wedges. It's a square mesh thing and it makes nice even crispy potatoes as the heat gets to the wedges evenly all the way round. It's a plasticy material (obviously not plastic though, not sure what it's made from) so it doesn't get hot and burn the edges touching it. It was from Dunhelm but I've seen them in asda before.
I parboil them then cook in a hot oven with hot oil.
But the best ones are the ones I pre-freeze, there's probably a sciencey reason. Basically, we don't eat a lot of potatoes so whenever I have a bag and want to cook some, I parboil the lot, then with the ones I don't want to eat I put them in a freezer bag with oil. Then the next time I want to eat them, just tip them into a baking tray with a wee bit of oil and for some reason they always come out lovely and crispy.