I have volunteered for many community-run conferences and I have organized two: GANG10 and Detroit Day of Azure. One of the challenges of a conference is getting people to attend. It's not enough to have great content. You have to spread the word about the event and you have to inspire people to register and to attend. If your target audience doesn't know about you event, they will not attend it.
Here are a few things my team and I have done to promote conferences.
Create a web site as soon as possible and keep it updated. This will save you time. When people ask for event details, you can point them to the web site. A Facebook or LinkedIn page is fine, but not sufficient because these sites are for members only and your audience will need to log before they can read all the information.
Create a Twitter account and post to it regularly. Have that Twitter account follow all your speakers and volunteers and ask that they follow it back. The new Twitter account won't have many followers at first, but you want followers who are willing to re-tweet what you post. Prior to the event, I would post to the Twitter account every day; then re-tweet from my own account (which had more followers). Because the promotional messages are coming from the event Twitter account, it feels less like spam to my followers than if it were coming from my personal account. Consider using a service like FutureTweets or an application like TweetDeck to schedule tweets in advance. This makes it easier to space out your tweets throughout the day. Be creative in your tweets: announce the speakers; announce some of the other perks, such as door prizes and lunch menu; talk about the venue; thank the sponsors. If you repeat the same message over and over, people tend to tune it out.
Make a list of people you think might be interested in the event and contact them. If it's a couple dozen, send a personal e-mail to each one or call each one; If it's several hundred, send out an e-mail blast. Services like Constant Contact can help with this.
Who are the influencers in the area that the conference covers? Offer them a free ticket to the event. Call them and let them know you'd really like them to be there. They will spread the word and reach more people than you could on your own. If they are talking about the event, that is great advertising.
Think of popular bloggers who would be interested in this event and tell them about it. Even if they can't make it, they may blog about it, increasing exposure.
E-mail your co-workers to let them know about the event. Ask them to spread the word among their colleagues, customers, and friends.
Print flyers. Hang them up in your workplace and in your customer's workplace and anywhere that your target audience congregates. Many companies have a bulletin board in the lunch room or break room just for things things like this. Ask others to do the same. Make sure the flyer has all the relevant information, such as date, time, and the web site URL.
Register the event at http://CommunityMegaphone.com.
Get others involved. Recruit volunteers. Not only will it help defer your workload, but those who are involved will feel ownership and will be more likely to spread the word enthusiastically.
Contact user group leaders. Ask them to promote the event at their meeting. Ask if they will send out an e-mail promoting the event. Some groups have a monthly newsletter and will be happy to add to this. If possible, attend user group meetings and promote the event yourself. Ask the leader if you can have 2 minutes to talk about it.
Send an e-mail to email@example.com. You will need to join this group first.
Create an event on Facebook and LinkedIn. As mentioned earlier, this is no substitute for a web site, but you may reach an audience that you otherwise might miss.
Contact the chair of the CS department of local universities and ask them to promote to their students. Consider offering a discount or free admission to students.
Contact podcasters and ask if you can be a guest on their show to talk about the event. I appeared on Community Megaphone a few weeks before GANG10 and this helped spread excitement about that event.
For Microsoft events, contact your local Developer Evangelist. They have their own channels for communicating with the local technical community.
I have done almost all of these things in order to drive interest in the event. The two key points are: let as many people know about the event as you can; and get people excited about the event.
Planning an event is a lot of work and a lot of fun. But the payoff is more satisfying if you have a good turnout.