1. Title Tag:

Type your targeted keyword phrase in ANY search engine and notice how 9 of the top 10 sites have that targeted phrase somewhere in their title tag.

*Learn from your competitors and remember keyword density and prominence.

2. Heading Tag Structure

H1, H2, H3, H4 and no more. Remember H1 is what the whole page is about and the other 'sub' H's are explaining each section under that heading. A good way to look at this is to look at it in a standard outline format.

A. = H1

--- a. = H2

------ i. H3

--- b. = H2

------ i. H4

------ ii. H3 & H4

--- c. = H2

------ i. =H3

--------- 1. H4

3. META Description

The META description is there to describe the page. So describe the page. Remember your page is about your targeted keywords. Make sure those keywords are scattered throughout the description of each page. Also, sometimes the search engines will display your description under your listings on the SERP's (Search Engine Results Page). Therefore make the description captivating enough to make the visitors want to click on your website and not your competitor's.

4. Age of Site

Arguably, this is the deciding factor when picking between 2 sites with great stats. Search engines trust websites that have been around for a long time. This is because if the site wasn't valuable, it would not be on-line any longer. Even though this factor is a huge factor, it's only a factor for old active domains. Old, yet active domains that have history of constant updates and consistently acquiring links are the hardest sites to beat.

5. Total Pages Indexed

The total # of pages indexed is very important because usually the more pages indexed the more keywords you will be targeting. This is not always true, however considering this is USUALLY true; this is definitely a factor in search engines' algorithms. The more pages you have, the more chances your site has to get found. Furthermore every page linking within your site (if done right) could build strong internal page rank.

6. Anchor Text of internal Links

It's important that the links within your site that leads visitors from one page to another describes that page with the keyword it's targeting.
IE: Get directions to our San Diego Location

7. Total Backlinks

YES, the amount of back links still matters. The more links you have, the better. BUT, it's the more relevant links from the greatest variety of sites, the better. You need links from blogs, forums, authority sites, educations sites, local area sites, industry sites, etc. They all must be relevant to you. The more accurate the relativity, the more closer you are to being the most relevant site to the searcher's query. The more (relevant) links, the merrier.

8. Anchor Text of Incoming Links

Originally if someone linked to your site, that someone was a different person with a different website giving you a link titling your company name. So if someone Googles your company name, you'd be the first to show up because other sites said that's who you are. But, new potential customers aren't looking for your web site. People are searching for your services. So you have to find ways to get links describing the services you offer.

This way other sites are vouching that you are "men's clothing". The SERP's already know you're Men's Ware House.

9. Average Time on Site

One factor that helps Google determine if your site is a site that will give visitors a pleasant user experience is to record how long visitors stay at your site. The longer you can keep a visitor on your site the more likely you are providing that user with an experience worth sticking around for.

10. Bounce Rate

Like Average Time on Site, Bounce Rate is a metric that measures the worth of your page. Do visitors come to your site and click the back button more often than not? Normally if 80% of the people visiting your site are clicking the back button, that site is not relevant to what they were searching for.

11. Strength of Competition

To be honest, this really isn't a factor in its own. The strength of the competition is probably the backbone of every factor. Ranking results are based on a comparative scale. Meaning the number 1 site is more relevant then the number 2 site based on ALL of these factors. Good ways to measure the strength of the competition is analyze their Alexa Rank, Total Pages Indexed, Total Backlinks and their Google Pagerank.

12. Total Character Count

The more content you have, the better chance you have at satisfying your visitor's query. Google looks for special keywords within your content to back up the keywords you are targeting.
If you are targeting men's clothing, Google looks for terms that will answer every visitor's query. Like pants, shirts, prices, location, xl, discounts, customer service, socks, fitting room, fabric, fashion, etc. Usually to cover all of the visitors' possible questions, you need to provide a lot of unique and informative content.

13. Page Rank

(Ceterus Paribus) Yes, page rank still counts. Many "SEO's" will tell you that this doesn't matter. But, the core of Google's algorithm is based on Page Rank.

14. Keyword Placement

Where amongst all of your content and web pages is your target keywords located? Keywords should have prominent placement in paragraphs supporting their matching headings. Naturally placing your keyword in rich related content the right amount of times is arguably the top ranking factor.

15. Types of Media

Have you noticed videos on the SERP's ranking higher than you?
Or, have you ever ended up at a site through a picture?
Having a variety of media types shows that you are presenting your targeted keywords in various forms, this is most likely pleasing a variety of visitors.

16. HTML Validation

Content : Code ratio is a ranking factor. It must be easy for the bots to run through your site. Also when spiders run through your site, it's necessary that you prevent any traps that could prevent the spider from crawling your site completely and finding all of your content. Broken links are also a big no, no. The bots hate getting led to nothing.

17. Navigation and Architecture

How your site is built and themed is very important for spider indexing and visitor navigation. The paths your visitors take are being recorded. So make sure the pages you want to rank well are easy to find for the user. Having your targeted keywords categorized and your page structure in a siloing format is best. Also add a site map to your website so the spiders could have a one stop page to your whole domain.

18. Click-through-Rate on SERP

Google wants to provide results the visitors want. And to help them determine what they want is to record how many times out of a 1,000 impressions do people click through to your site. If your listing has the highest click through rate it must be because your title, description and or brand are what the users was most likely looking for. This is why title tags and META descriptions are 2 of the other 20 factors in ranking well on the SERP's

19. Total Search Queries Conducted After Leaving Site

If the user searches for that same term over and over again, they must not have found what they were looking for. Your site should answer the visitors query by proving data to the engines that proves that visitor don't need to look any further.

20. Percentage of Return Visits

The higher percentage you have of returning visitors, the better. High return rate means people who have visited your site before enjoyed their visit and found your site valuable. This factor is used in helping Google help others find a site that the visitor may find interesting. So if your site is relevant to the searcher's query and everyone that visits your site returns, Google will use this as a measure of a relevant and interesting site, thus leading to search engine higher rankings.