Make sure you have all the common tags they look for (certain meta tags for instance), having meaningful keywords and content, and get traffic to the site. WP has a few plugins for analyzing the content and setting up the required meta tags, and there's a few sites that can analyze a web page for such as well. Most "SEO" services and programs you find nowadays claim "get your site on 1000s of engines" and "get free traffic!" and such...they're all snake oil though, and some can actually hurt your rankings because they effectively spam your site across the internet to get that traffic. If you're considering these products...don't waste your time. Beyond that, the best advice I can give is to let it take its natural course.