Ideally, you should contact an SEO company that specializes in real estate web design, or at the very least, is familiar with the needs of a realtor.  Most of you will need to have MLS Listings on your site, and many small web designers will not know how to implement this on your site.   In the beginning, it may cost you a little more to have a real estate SEO company do the site design, but in the long run, it will usually cost you more to hire one afterwards and probably have to have the basic site design re-done.
It's a little known fact, but up to this point, colleges do NOT teach search engine optimization in their web design courses!   Hopefully, that will change eventually, and new graduates will know how to do it correctly.

Reciprocal linking on interior links pages NO LONGER WORKS!   Hiring an SEO firm to do this will be like throwing your money out the car window. This has recently become ineffective in most search engines, and even incurs penalties in Yahoo now.  It will take a long time for the SEO companies to stop doing this, because it was a steady, monthly income and charge, and they could hire kids off the street to perform it.   There are still services that offer to "Add your website to 500 search engines", and this practice has been obsolete for close to 5 years!

• DO NOT HAVE A FLASH SITE!
  DO NOT. DO NOT. DO NOT.

Can I emphasize that any more?  Search engines do NOT index flash presentations.

Flash is a movie. A search engine spider or program can't watch a movie.   If you must have one of those beautiful fancy flash sites, then resign yourself to paying for pay-per-click advertising and find another topic to read about.  However...

You can EMBED a flash presentation inside of a regular webpage, and it's treated like a photo or any other kind of graphic.  A good designer will know how to do this.  Insist on it!

• DO Have Plenty of Text on Your Homepage, Using Your
  Search Phrases Sparingly

Most of us agree on 250-300 words on the homepage.  You might get by with less, and more could be even better.  Google's sweetheart of a rep, Matt Cutts, told us at one of the SEO Seminars that you should limit it to 1000 words, or the main topic of your website might be hard for the search engine to determine.

Pick one or two of your most important search phrases for the homepage and write about them.   You simply CANNOT rank a homepage for every real estate search term in your area, so decide what is most important, and aim for no more than 2 or 3 key phrases.   Most of the time, the phrases will be something like Myrtle Beach real estate, or Myrtle Beach condos.
Your inside pages should be optimized for the secondary phrases, and as your site gains in age and importance, those pages will show in the search results as well.

• DO NOT Use Your Key Phrases Excessively

Especially with a competitive search term, for instance, "Las Vegas Real Estate", Google has some sort of filter that blocks your site if you have your keywords on the page too many times.  How many is too many?   The general consensus is about 2.5% of the text. That means if you have about 300 words on the page, then you can only have it on there about 3 times, max.   I usually have a header tag, one of the ALT tags, and maybe once or twice in the general text.  I usually also have 400-500 words on the page.

• DO Have Your Navigation On Each Page In Plain HTML

If you want to use little graphics for your navigation buttons, or fancy DHTML or Javascript Mouseovers on your website, then be sure at the bottom of each page you put the navigation again...in plain text HTML anchor tags.   Although the search engines are becoming more able to read javascript and you can put ALT tags with your buttons, it's still better to add it on in an easy-to-spider format.  Serve up a few insects to those nice spiders you want to visit! :-)

**Extra tip** If you can do so in a natural way, try to label your navigation buttons to mention your keyphrases.   Don't overdo it, but instead of saying "Home", why not say, "Sarasota Real Estate Home" as the anchor text?

• DO NOT Use Any Of The Old SEO Tricks From Years Past

Don't even think about hiding text by coloring it the same as the background.

Don't create several sites and have links to each of them on every page of each of them.   In fact, recently, I've seen sites banned from Google and Yahoo both for trying to fudge by using any site-wide linking strategies to artificially increase incoming links.   In the early part of 2006, it is becoming apparent that even reciprocal linking is now on the way out.   Your best bet is avoid interior links pages and "directories", and concentrate on one-way links, like Press Releases, Articles you've written, and informative real estate blogs. **Hint** Buying text links on big sites to increase your Google Page Rank doesn't work anymore either.

Don't have more than one domain name with duplicate content.

Don't have more than one domain name and use a javascript or other "re-direct" to try and get your website indexed more than once.

Don't use CSS or javascript and try to hide text containing your keywords.

Don't put a bunch of garbage text at the bottom that says something like: "This site contains information about Los Angeles Real Estate, Los Angeles Homes, Los Angeles Condos, Los Angeles Houses, Homes in Los Angeles, Property in Los Angeles Yada, Yada, Yada..."   If it's found out, you can get penalized.

Don't slather every picture on the page with your key-phrases.  If you can inject a bit of a phrase into the picture's ALT tag description, then that's a plus.   Using it over and over and NOT describing the picture is bad news.   ALT text is supposed to be used for the blind and for browsers that don't display graphics, so the reader will know what the picture is about.   Don't assume the spiders are that stupid.

• DO Build Your Site For the User, Not the Search Engines

Even if you manage to get your website indexed and ranking high on a given phrase, it won't do any good if your site looks like a billboard for "Real Estate Hooked on Phonics".

A person looking to find a reputable Realtor to buy or sell a home is going to take one look at a website that says "Miami Condos" 57 times and think you are either a flim-flam, or you have a stuttering problem.  Your bottom line is still to convince the user to call YOU.  If they click on your site because it's number one in Yahoo, and all they find is a bunch of stupid sounding text and phrases, they are going to click right back to the search and go to the next site.   And it's said that the engines can record this kind of activity and lower your rankings if it happens alot.

Make your website attractive, easy to read, easy to navigate, and interesting to your reader FIRST, and then tweak what you have to, to attract the search engines' interest.   If you do that, you'll be one step ahead of your competition every time.