The following is a list of best practice associated with SEO and appropriate questions to ask when viewing a competitive site. This list is by no means exhaustive but acts as a good starting point for comparing the SEO practices adopted by competitor sites:

URLs

Are they nice and short and contain keywords?

Title Tags

Do they contain keywords & brand? Do they change between pages?

Meta Descriptions + keywords

Does the description contain a call to action? Does it change to reflect page keywords?

Dynamic tags

Do the tags appear to be dynamically generated?

Anchor text/Link Text

Is there keyword rich copy (anchor text) across site? Is the link text keyword rich and does it match the title of the page it goes to?

Keyword targeting

I.e. do they do a 'hot products' list or 'popular products/destinations' links which you can click on?

Header tags

Do they use Header Tags? i.e. H1 tags & H2 tags

Alt attribute tags

Do they use targeted keywords to label the images?

Crawl maps

Very effective for large sites to ease of navigation

Site maps

Does the site have a sitemap to aid spider and user site navigation?

Robots.txt file

Does the site give instructions to spiders for what pages to search and not to search?

RSS Feeds

Does the site offer industry news feeds to keep content up to date?

Content

Do they have extensive product/category/information pages?