Search engine optimization itself covers a vast amount of topics and procedures (which is why most professionals and businesses leave it up to SEO firms), and it would be utterly pointless for me to get into all of it now (and very nearly impossible). But there are a few key things that will be very beneficially for you to know. Even if you can't perform the operations yourself, you'll at least know exactly what to ask your SEO specialist when the time comes!
There 5 little tidbits that I'm going to divulge which will do a world of good for any website owner to know. The first 3, called META tags, are normally grouped together. These are the foundation of your site, the title tag, description tag and keyword tags that are necessary to draw the attention of the search engines. The thing to understand about these tags is that they aren't visible to you, me or your website visitors. They are a part of your website's invisible structure, but a very important part and the starting point of SEO. Your title tag will give your website a title. That's the initial factor that tells the search engines and your visitors what your site will be about. Every well-developed website out there (perhaps with the exception of the search engines themselves) has a title tag. The way it'll translate to you, is the topmost bar of your web browser , like below:

This tag describes in shorter words what your website offers. We can tell by this tag that Paypal offers merchant services and credit card processing. Your title tag needs to be just as descriptive - direct and to-the-point! Your description take should be no longer than 200 to 250 characters, and describe your site and services in a bit more detail. And your keyword tag should list every keyword that you feel is relevant to your site's content. A good rule of thumb is to take your most important 2 or 3 keywords, and make sure they're included in the other 2 tags, as well as your site's content.
Next is your sitemap. Few know that importance of this feature, but trust me when I say it can make all the difference between your site being included in search engines in 6 to 8 weeks or 2 weeks or less! Your sitemap is just a graphical stucture of your website, with clickable links that make it easy to navigate your site. But it's not just for visitors. Your sitemap can actually be submitted to search engines for separate indexing, which helps your site to be included faster, and rank higher! There are several programs out there that will help you create the kind of sitemap you need for submission to search engines, and your designer should also be familiar with how to create this (so here we have yet another questions to add to the list: Will you be creating a sitemap for my site?). I suggest XML versions submitted to as many of the search engines as possible!
Now, the last are the "alt" tags associated with images on your site. Attaching an alt tag (just a short description of each image) that contains your main keywords can greatly affect the ranking of your site. I suggest a web design do this with each image on the site, including (especially) logos, header images and the other forgotten structural images. This will increase the keyword density on your pages without your ad copy being flooded by a few of the same words ( that's a pretty noticeable and tacky way to increase keyword density). Not to mention, more and more people are doing searches for images these days. Imagine that you have 100 images on your site, and all have been equipped with alt tags. Each time a person searches through images on a search engine for any of those keywords, all of your images will show up, linking back to your site. That's 100 times for a person to be introduced to your site (especially if they like your images).
There's a whole lot more to SEO, but these should get your started (and give your designer enough to do to earn their pay)! You have to start with a structurally sound website that will draw potential customers in and keep them there. So our two main focuses throughout this blog will be getting them there, and keeping them there. Part 3 of this series will cover the remaining basics of web design and SEO. If it's all greek to you, just send your designer over because the basics have to be covered to get the rest going! Happy webmastering!
