Hi mghFond,
We've played a few to completion here over the years. I think the tricks of the game are as follows.
1. Number of players:
Keep the number of campaign players as low as possible and confined to those who are really keen to play and put the time in. If you have spare players, give them the roll of subordinates (reserve stand in player to cover holidays, etc.), or as table-top commanders who can flit from one campaign faction to another and who play for their own victory points (for winning in battle) in a sub-league.
2. Campaign length:
Give the campaign either a definite length in turns (the campaign in this post will last a season of 16 turns) or a definite set of campaign ending victory conditions that are achievable in a reasonable time. Knowing when a campaign will finish is a great boon in keeping people going to the end.
3. The law of KISS (Keep it simple, stupid): Don't bog the players down with running economies, running logistics, or endless complex order writing. As a game designer you might like this kind of thing, players tend not to – boring, boring, boring.
4. KISS me again:
The rules of the campaign should be no more than half as complex as the table-top rules you use. Players use campaign rules so infrequently that they tend not to 'take it all in'.
Make the rules for movement and orders simple – as the umpire you can prod, advise and amend for the rest – so that the players can get going quickly.
5. Email:
A wonderful invention for quick campaign move turn-around. Set up a file with sub-files for holding the orders of each player, contacts and chit chat.
As umpire, don't insist on being kept informed of anything outside of your remit – what players cook up between themselves is up to them – because you will have enough to do.
6. Blog / Website:
Set up one if you don't have one. Use it to keep players informed as to campaign progress – the campaign diary on line. Move plotting and battle reports on what is generally known.
Make sure your map can be photographed at the end of every campaign turn. Put this up so the players can use it to plot their next turn / orders. That way they don't need to keep one at home if they don't have the room or safe place to keep it.
7. The unknown:
Keep what has to be secret to the minimum. Work on the principle that it's very hard to keep things like the movement of armies secret, especially pre-20th century. It's all part of the KISS thing.
Only my two penneth's worth, picked up along the way.