A hierarchy I find is imperative; I’ve been involved in countless factions over the years and have led a majority of them – I’ve found democracy isn’t as productive as a dictatorship! But the dictator has to delegate. As Relonor said it shouldn’t be reliant on the leader, delegation so characters can pursue faction goals without oversight is the key.
Distinct goals – and I typically find PC orientated goals to be the best for a solid foundation. The faction needs a clear direction and several projects to undertake at any one time so any member can delve into something if they’ve some free time to kill.
Conflict. If you promote within the faction a rivalry or conflict with another PC entity your members will always have an outlet for some intrigue and PvP – There’s so much to do with feuds that chews up a lot of time and proves – in my opinion – the best part of the game.
Membership. Proactivity – or a lack of, kills PC Factions. You need to get your name out there and recruit, recruit, recruit! I’ve always favoured the easy to join, easy to get kicked out approach in that regard. Welcome players on board willingly, if they’re not pulling their weight – get rid. I’ve found half a dozen active contributing players to be sufficient enough to be true influence on the server.
Keep the DMs up to date with your plots and plans, accomplishments and goals. If you’re shaking the server and you’re out doing things, involving people and the DMs are familiar with your concept and what you want to achieve you’re going to be getting DM assistance.