Here are some tips for you!
• Get Your Apps On Blogs - Contact reviewers. Most will do it for free, some will charge for the time spent. Even GiveMeApps does promotion services. Contact them
• Social Networking - Your app should have a FB page separate from your personal page and even the pages of your other apps (the more presence the better, promote them everywhere)
• Reviews - Read #1. GiveMeApps works fast on reviews, but there are a billion review sites. Paid reviews get your stuff up faster with more promotional effort on behalf of the reviewer
• Videos - Your app should have a promo video on YouTube. Everyone goes to YouTube!
• Word Of Mouth - You should be talking about it to anyone who listens