Both the age of your website and the age of the incoming links factor in the ranking of a website.   Thus, it's important to have some patience in this department.

It usually takes years before a quality site becomes highly ranked in search engines.  Get a working version of your website out as soon as possible so that it can start aging.  Then, add content that will make it valuable.

Also, start getting established websites to link to you.  This may cost you, but it will help you in the long run.

The total number of incoming links benefits you in two ways.

First, if users are on those other sites, they may want to browse over to your website.  You'll want to provide them with useful information or services.  Take advantage of that easy traffic.

Second, search engines value incoming links.  It is believed that if your website has important data or services, many websites will want to link to you.  So, search engines will put you at the top of searches that look for your data or services.

Quality links are links from other websites with a high ranking.  In a way, its like if an expert recommended someone to you, you'd listen to their advice.

The more experts recommend you, the more clients you get.   So, search engines are taking the advice of these other websites and moving you up in their ranking.

It's important to take advantage of your own website.

Try to focus your ranking on a couple of key pages, such as the main page or your best selling product page.  That way the search engines will put them on top of key searches.  Make sure you keep the links consistent.

For example, if you have a default page and some links point to http://www.domain.com/default.html, while other links point to http://www.domain.com/, you'll end up splitting your PageRank among those two links.

Some search engines view those as two different links even though they end up at the same webpage.