1) Make sure the community is fully functional (website wise) before inviting anyone.
2) Be ready to have a first challenge up and ready right off the bat to give an example of what's to come.
3) [Optional] For quick members, find people who are members of similar communities and post a nice polite personal-sounding invitation on their private journals.
4) The usual way of recruiting is to post on the promotion communities.
5) An additional method is to offer affiliation with the bonus of spotlighting (with benifits) to the communities who are nice enough to publically announce your community to their members in a post. In my communities, I offer a pack: If you spotlight us we'll spotlight you AND add you to the user information as well as our post-affiliate list.
Once you have members ...
1) BE ON TIME. Nothing is more of a turnoff than contests that are never on time.
2) Say no to extentions. 90% of the time, if people don't add to a contest it's because they don't like the challenge and making it last longer will only turn them off.
3) BANNERS. 80% your members are banner collectors. If you're late with them, they might leave depending on how late you are. Never wait over 2 weeks for banners.
4) Be polite. "The customer's always right" isn't necessarily what we're striving for, but being diplomatic and patient will get you farther than being a smartass. Yes, you run the community, but without the members you won't have an icontest. If someone has a problem (picture chosen isn't good, etc) don't take it as a personal insult. Keep an open mind and if you can't answer without being on edge, wait a few hours before addressing the situation.
5) Make the members feel like they're important. Get feedback! Be it asking the members to vote on a way of voting (haha, I know, confusing) or winners choosing the next contest or ... whatever else you can think of. Make them PART of the community instead of just entering to it. If they feel more of a connection, they'll be more loyal.
6) Reminders! People could use reminders. Midweek and last day reminders are usually best. When you post reminders, don't growl at your members if you don't have the amount of entries you want to. Getting upset "come ON people, we need more entries!" will only turn off those in your community and might cause people to leave, rather than enter. Even if there are only 3 entries, go forward with the voting ... as long as there are only 2 entries there can be a winner.