Listed below are simple steps you can implement in your website so your customers can find your products and services from any mobile device.
NAP. Name, Address and Phone Number is one of the most important pieces of information you can add to a web page. This is self explanatory why you need this, however with mobile devices they can click on your phone number to call you from their mobile device, this is called a "call to action". I recommend adding the NAP to the footer in your website so it shows on all pages.
Responsive Website Design. This is how your website renders your content on mobile devices. Having a responsive site ensures that your visitors are served content that is readable, properly displayed and easy to navigate. Most Content Management Systems do this automatically for you, however you may need to implement a script. Here is a link to learn more: Mobile Redirect Script
Geo-Tags. Geo tagging your website and pictures allows your location to show up in search results when someone searches from a mobile device. You can implement Latitude and Longitude Geo-Code in Schema so it can be properly recognized by search engines. Picasa also allows you to Geo-tag your pictures. to learn more visit here: Geo-tags for local Businesses
Pictures and Video. Some mobile devices do not support flash. If you have flash content you can use HTML 5 standard tags to embed the video. I recommend staying away from flash as it slows down the page load speed. It is recommended that a page should load within 1 second on a mobile device depending on your connection. Pictures can be Geo-tagged using Picasa (link above). Pictures should have alt-image tags with proper descriptions of products and services preferably with location in the description.
Short-tail Keywords. People searching on mobile devices generally tend to put in keywords that are shorter in length as it takes more time to type on smaller devices. Put these short-tail keywords in the meta tags, header, body and footer.
Sitemap. Add a mobile XML Sitemap to your website. This gives page Hierarchy telling search engines which pages are more important and also allows for easier indexing. You can add a Mobile Sitemap here: Mobile Sitemap Generator
Maps. I prefer to use Google Maps. Make sure your pin marker is on the correct address. You can embed the map into any given web-page using a snippet of HTML code provided to you. You can add your business to here: Google Maps
Socialize. Add a social sharing widget as well add the links to your social networks. The more people that like or recommend your pages increases the links pointing to your mobile site in return helping to improve the rankings for your website in the organic listings. Social search is being integrated into search results so sharing your content and posting to your networks will send important social signals thus helping to increase your mobile website rankings.
Resources: To learn more about Mobile Website Guidelines please visit Google