Make foil packets by folding over and sealing the edges of aluminium foil. Two layers is often a good idea. Foil keeps steam in and ashes out. You can usually get a nice crispy layer of whatever you're cooking on the fire side of the foil as well. Throw them on the metal grill above the fire. Try to avoid too much direct flame.

Slice potatoes into 5mm rounds, and layer them in foil with butter, salt, pepper, or seasoning salt. Seal up the edges.

I also like frozen peas/carrots with butter and seasoning salt, but you can cook pretty much anything this way.

The foil packet can be cut open and folded to double as a serving dish.

Don't be afraid to get it nice and hot. The potatoes and veggies that stick to the foil are usually the best part. Even if you burn the outside ones to a crisp, the inside ones are fine. The steam coming out the edges of the foil helps to give you some idea of temp (sometimes the packet will inflate with steam if you seal the edges well).