1. Dont Cheat the members.
if your intention is to scam people please keep it out of guilds. The best guilds are the ones that are composed of a network of friends- linked with trust.
2. Try to get a good friend to go in it with you.
Running contest, coming up with fresh ideas, recruiting members- its a big challenge sometimes, and if you have to leave for a week- you want to know that someone is keeping it up and running. 
3. Be persuasive, if you aren't, you can't run a guild. If you are the leader- everyone should know you, talk to you, have your aim, and vise versa. Persuasion is great for getting excellent members! when you get one, you can use them to persuade others to join. (this works well in Themed guilds- bd/sniper/restocker- go for the legends)
3. Have lots of contetst. I dont care how 'nice' you are, or how great your friends are, people like contest. People like free stuff. People like winning/bragging rights.
4. Have a theme. Its way easier to have an active message board if everyone has something in common to talk about. 
5. Get a Great layout. Pay for it, Spend 12 days and nights on it- Layouts are the First thing people see when they join your guild, and having a free one doesn't say much as to the effort that a good guild should have. 
6. Pick 'pretty' council. The second thing that people look at is the council, the sub council- their accounts, are they rich, are they cool/handy friends. 
7. Acknowledged all members. No one likes to be ignored, run member of the week- in the news mention peoples birthdays, personally go out of your way to neomail people happy bday- make gifts, randomly give things for their gallerys- be friends! Even if someone is annoying... dont seclude them, ignore/kindly warn. I recommend rotation sub-council inorder to let the members who you would Not want to give council, yet dont want to leave- a reward. 
8. Watch out for your members. Don't get your account warned! Don't make people pay to be in contest, etc. Follow all of the neo rules, dont let scammers in. If someones shady call them on it. 

9. Think about your target crowd. If you are running a restocker guild, dont have newbie packs/give omelletes for xmas packs- These people are rich. You have to work extra hard to please them. If you want a monsterous guild, throw 1 np (nf only with no neofriends) auctions, DONT block nf request-simply have a 'join my guild' banner on the front page. 

End Note: Owning a guild and running it is tough. It takes up alot of time that you could be spending on bd'ing/making nps/other stuff. You make a commitment when you create a community like that- make sure that you can really handle it.