How can I control the heat when cooking on a campfire?

The key is mostly to cook over coals rather than open flame if you want decent control. This is a principle you find all over slow smoking/BBQ. You start the fire with plenty of wood and let it burn down to a pile of red coals, which you then can cook over with nice control.

Personally, when I want to cook over an open fire, I treat the fire pit as 2 zones: fire and coals. I use the "fire" side for anything where I want an open flame, like roasting marshmallows or hot dogs. As a chunk of wood on that side of the pit burns down to coals, I move it over to the other side, for more controlled cooking.

Another way to handle the variability in campfires is to cook with things with a lot of thermal mass to even the heat out. In practical terms, that boils down to cast iron and clay/ceramics. Whether it's a dutch oven or a little "cave" of fire bricks, these materials spread the heat out so nicely you can often just bury them in the coals and "bake" or "roast" a lot of options that you might not have considered as "camping foods".

The same is true of other cast iron pans and much of the stoneware from places like Pampered Chef, meaning you can pan fry, saute, and do many of the other more typical "kitchen" tasks over a campfire.

One word of warning regarding this principle though is that it might seem like collecting rocks from a nearby stream to use as the thermal mass is a good idea. It is not. Rocks that have spent long periods under water can crack and/or explode when suddenly heated up.

Not sure how much equipment you're hauling, but my advice is to employ aluminum-foil generously. Once you get a nice sear on your meat or kebobs, cooking over direct flame will only dry-out the meat. Wrapping food in foil helps evenly distribute heat, and it keeps moisture and juices inside the pouch. I particularly like sausage , onions and peppers done this way. Just make sure to double-wrap the foil, in case you get a tear.

There are so many variables here, I can't address them all. Whether are not you are hiking or driving to the camping spot, whether you can bring frozen/refrigerated ingredients in a cooler, whether you have permission to modify the camp fire area, etc.

If you are hiking a fair distance, you will need to stick to safe-at-room-temperature ingredients, use light cooking implements (no cast iron pots).

If you're driving right to the camping spot, you can bring more and heavier cookware, a steel rod to put across the fire to hang a pot from, a grate for BBQ and frying pans, a cooler for frozen things.

If you have permission to set up/change the campfire area, an ideal shape is like an old fashioned keyhole, surrounded with stones. Point the slot towards where the wind is coming from, and put flat rocks of equal height on either side of it. The slot is also where you will rake the coals to, and put the grate on top of for any frying pan/sauce pan cooking. Food wrapped in aluminum foil can go into the coals underneath. Coffee pots and dutch ovens can hang from a steel rod put directly across the fire.

It's important to remember that you're going to need to be cleaning dishes, likely without running water. After you scrub food out, you can sterilize pots by reheating them after the meal.

Take local wildlife into consideration. Avoid too many leftovers to temp raccoons. If you're in an area with a lot of bears, reconsider that rotisserie chicken idea. ;-)

Other than that, imagination is the limit. You really can cook almost anything over a good campfire.

Another great idea I've done before when portaging (i.e., in the situation where you want to travel very light) is aluminum foil envelopes filled with a fish fillet and veggies (sugarsnap peas come to mind). Bring the fish fillets deep frozen, then they should stay frozen during the first day if you insulate them well enough from the sun (e.g. wrap them in multiple layers of the the aluminum foil you need to bring anyway) and you can prepare this stuff the first evening. To make the envelopes, just fold a sheet or two of (extra strength) aluminum foil in two, then double fold a 1cm strip on two opposite open sides. You now have a pouch that you can fill with goodies. Double fold the remaining open side and you should be good to go.

In addition to what everyone else has said:

Roast root vegetables are a really good idea. Squash, parsnip and sweet potatoes are usually nice. Wrap them in a layer of tinfoil and put them in some hot coals and leave for an hour or two. If you cut them open first you can put in things like butter, honey, dried fruit and so on, but they will sometime start leaking!

Flatbread is always good as a side or for desert. If you mix the dry ingredients (flour, baking powder, salt) before the trip, you can take it with you and just add water and oil the evening you're cooking. You can cook in a pan or on a flat rock, or you can wrap it around the end of a stick and roast it like a marshmallow! (recipie here, though I can't vouch for the quantities)

In a non toting-the-hardware-on-your-own-poor-back context, you can't beat cast iron. Dutch oven, skillet, and griddle. This will even allow you to cheat a little (but only a little!) on the coals not flames advice.

With these tool you can do some serious cooking, limited only by your prep-space and ingredients on hand: you can even bake by putting a second vessel in the dutch oven (use pebble or such to prevent direct contact with the hot iron.

You can do just about anything on a campfire -- even some baking if you're willing to carry a dutch oven.

The important rules to cooking over a grill or campfire it so be prepared to move whatever you're cooking to a lower heat part of the fire (this might require bringing fireplace gloves with you), and to not turn your back on it for too long unless it's over low coals.

I've done curries (onion, chicken, coconut milk, green apple), stew, pasta, chilli ... you can do most anything.

For the kebabs, I'd recommend turning them regularly, and not mixing the skewers -- make them all meat, or all a given type of vegetable, and mix afterwards. You don't want a bunch of singed vegetables next to under cooked meat.

One option to consider it to make "dirty steak". The basic idea is to burn the fire down to a bed of hot coals and then just put the steak right onto the burning coals. I have done this with a London Broil and it works out very nice. It sounds crazy but the steak really doesn't get dirty nor does it burn up like you might think. The lack of oxygen a small bit of juice from the steak seems to make a nice interface between the steak and the coals. There are a lot of interesting articles on the web:

http://www.google.com/search?hl=en&source=hp&q=dirty+steak&btnG=Google+Search

It's great, you can hike with a frozen steak and have it thaw during your walk. There is no pans or other stuff to clean and it's super easy.