Here are a few factors that can affect your search engines ranking and also how visitors use and interact with your site. They are easy to fix and some are problems webmasters have in the beginning.

Sitemaps

Your site needs to have a sitemap for both your visitors and the search engines. Some visitors find them useful if they can easy find a page they are looking for. The search engines use sitemaps to find new pages on your site which they would have not found.

Analytics Page

Setting up an Analytics page is free and it tracks all your visitors to your site. A very handy and useful tool.

Flash

If your site is all in flash or on the page you are trying to rank is in flash, or all images then the search engines will have a hard time indexing these pages. It may look good to visitors but it is useless for search engines.

No Text

This falls into the previous category, if your site has no text then the search engines will not know what your site is about. As the search engines use the text on a page for a factor on how to rank pages it is very important to include text and stay away for flash.

Robots.txt Files

Using robots.txt files with command "no crawl" will tell the search engines not to crawl a page; if you tell them not to crawl a page then they will not index them.

Headers

Using text in the header of your site is better if it is in text rather than an image so the search engines can read it.

Duplicate Content

Just using someone else's content will not get you ranked high. Google looks for unique content and the site you stole the content from will out rank you for that content anyway as it is the original source.