My CV on this is clear and extensive.
I participated in four campaign games, two of them run by Bob Wall and the IWG's by Ted Haskell and Ed Miller back in the 60's and 70's. These were quite good.
I created and ran seven of this type of campaign. Big huge IWG's and many smaller ones. Made and designed the maps for them all.
I ran four play-by- mail games for profit back in the 80's "Cluster," (Sci-fi) "Bron-" (Prehistoric, but no dinosaurs). Baroque (17th century both imaginary and historic version, and "Clustron," a computerization of" Cluster" Baroque in both versions was computerized completely- I designed and wrote the code programs my self. Very detailed deep games. Baroque also printed out automatically battle reports.
I have experimented with about a dozen means of running campaigns, and have finally developed an excellent system that seems to get around most of the difficulties.
Dragon gunner has given a lot of good points. However he has soft pedaled it.
Most of the people who say they want to play in your game simply want free stuff. 80% of those who show interest you will never hear from again once you've sent them the game materials.
Of the remainder 10% will belabor you with bull crap, usually of the "YOu have this rule all wrong, you should rewrite it like it is in "Empires, Ego's and Liars" or "Napoleon's Buttons." but never send in more than their initial dispositions if that and 5% will quit after one turn even if they haven't had a battle because they're just plain lazy. A further 2% will drop out if they even lose a eensy-teensy battle, and 2% will drop out because their cat has a conniption, or some other excuse. Only 1% will be in it for the long haul and fight on through thick and thin.
After years of this I finally developed a campaign system which I call "Functionaries, Flunkies, and Munchkins." The system works extremely well and each player is the head of a country and quite free to do whatever diplomacy they wish.
The game is designed to be completely independent of players. The players get NOTHING of the rules or materials, just a short folio of twelve pages long. There is NO record keeping for them to do, no strategies to plot. All they have to do is send in an "intention" of 20 words or less (no abbreviations) of what they wish to do that turn. If they don't send it in the FF&M do it for them, representing the rest of the state.
The real game is a "GM kit" with all the materials to do the record keeping by the umpire in a fast and efficient manner. With twelve people this can be done in two minutes per player, and they can be as "soldier kingery" as they wish. Most however are just too bone lazy to do anything.
I don't send them any game equipment because they'll lose it, I don't send them any rules because they won't read them, and I don't expect them to remember anything because they'll forget it.
Yet.. the campaign is still going on and has been for almost 3 years. Further, all battles are resolved on the table top.
Oh yeah… if you are doing this. CHARGE THEM! This will save you a lot of money by eliminating the wimpy's "I would gladly pay you Tuesday for a hamburger today"-- the guys who only want freebies, and it makes them have a stake in the game. I have run this campaign for this time with my home basement group, and we've had about 20 battle so far.
The game mechanics are the key to the success. I noticed that if you tie the campaign to table top battles, the dears have an interest in that, and it has meaning to them. They will come and play, though they will forget about everything by the time of next months game. Not to worry, the game takes care of that. I also solved the problem of losing a battle badly as the victor of the battle gets victory points and the loser loses nothing. There are also means of having specific personalities for different kings, role playing, skullduggery, and slander and diplomatic attacks against sovereigns.
It all works extremely well, everyone has fun and are pleased they don't have to do any work. The game literally runs itself and there is no need for even computerization.
The logic of the game is simple. It relies upon a careful design of where the player "enters" the game. The player "enters" the campaign game as "the sovereign" and makes the big decisions that a King does for the campaign. Then he steps out of the game and "re-enters" it when a battle is engendered. Here he enters as "The General" of one side or the other. Think of yourself commanding about one third of the army, left, center, or right.
Everything between the "King" and "the General" is handled by the "Functionaries, Flunkies, and Munchkins," who take the orders you have made in the intentions and go off and like good obsequious little moles- work their fingers to the bone in setting in order what you wish to do. These are also the people you get to blame when anything goes wrong with your God-like plans.
And now for the best part. ALL the record keeping and the WHOLE game, every last piece of it fits into a box 5" by 4" by 9" long. Its all there. Nothing need be set up, taken down, or left somewhere where it can be disarrayed. you can't lose the parts.
If you think I am being unreasonably harsh, I'm not. These are my dearest wargaming buddies who I've gamed with for over 20 years. They're not in it for work, or stress, or difficulty. They simply want to progress from easy victory to easy victory and if they lose have someone wipe their ass for them. Just because they are my long time friends and buddies doesn't mean I wear rose-colored glasses.
I knock myself out putting on games and inventing these systems for them because their my friends and buddies and I want to show them a good time even though sometimes they're like puppies in a park romping about till one of the bubbles a young girl is spreading around pops on their nose and causes a brain fart for a few moments.