Getting local businesses, that you work hand in hand with, to promote you can increase event attendance significantly. Getting them to promote on their website, in a news letter or having flyers on the counter if their business has a shop front can be huge. In return you can offer web based promoters a link from your site to theirs, which directs traffic and business to them, or offering advertising at the event is another way to appeal to them. You’ll want to go after the big whales and companies you think will bring you the most success first. Make a list of targeted companies and work your way down the list till you have either as many as you can, or your target amount of publicity. Make sure to not over sell advertising space to your event as this may be frowned upon in the future, making them not want to do business again. Like i said, make a target list and knock them off in order of importance.
Guest speakers can bring a draw of their own. Help them help you. Get them to make it well known that they are attending this event. Bringing more eyes to you and more eyes to them cant hurt. Get them to reach out on social platforms as well as any chance they have really. Do the same back for them. Scratching each others backs can go a long way, in the short, and long run.