Search engine optimization experts come in two different types—those that focus on analysis and those that focus on implementation. Few sites need experts to help them with implementation—but many sites can benefit from expert analysis.
Search Engine Optimization Expert Implementation
Do you need Picasso to design your site’s layout, or Hemingway to write your blog posts, or Caples to write your ad copy? No. Your site works just fine being created, written, and advertised by mere mortals. 
Hiring a search engine optimization expert to write copy on your pages is overkill. Worse, it benefits one part of your business by risking the rest of the business.
A search engine optimization expert will get your site higher rankings in Google and other search engines, but he might sacrifice your sites’s readability or selling strength to do it. What good is it to your site to rank high but sell poorly?
Search Engine Optimization Expert Analysis
On the other hand, hiring an expert to analyze your site makes perfect sense. First, you only need a few hours of the expert’s time, so the cost is much lower. Second, the expert can point out your top flaws, so you concentrate your effort (or money) on the main problems. And, third, you can much more easily choose between effective SEO and your other business interests.
Remember that many search engine experts make a significant amount of money from add-on billables. For example, they’ll tell you what is wrong with a particular page as part of your contract—but then they’ll offer to rewrite the page for an additional fee.
There’s nothing wrong with add-on billing, but be careful when buying. You almost always get more value for money by updating your own content so you fully learn the lessons taught by the search engine optimization expert. The experts know this, so they’ll often use time pressure to get you to make a decision quickly—they’ll indicate their time is limited or offer you a special deal. I recommend that you always wait 24 hours after talking to an expert before you buy any additional products from him or her so you have time to think through the situation.
How To Find A Good Search Engine Optimization Expert
Search engine optimization experts come in two varieties: core experts and edge experts. Core experts focus on core search methods, such as those recommended by Google. Edge experts focus on cutting-edge methods, including those which might be called blackhat search engine optimization.
Unless your site is in a hyper-competitive niche, you want a core expert. (And if you are in a hyper-competitive niche, you might want to consider trying one of the millions of less competitive niches.)
Edge experts often recommend techniques which will only improve your ranking slightly, but which will put your site at increased risk of being banned from Google’s search index. This is highly probably after the recent Google updates. That’s obviously not good for your business long-term, but—remember—the consultant probably cares more about impressing you short-term than about the long-term health of your business. He or she won’t be there when Google drops your site.
BONUS VIDEO: Listen to Matt Cutts as he answers the question: What Should We Expect In Terms of SEO
