You really should try reading some of the threads in this forum - both these things get covered over and over and over again, day in, day out.
on-page factors: 1) keywords 2) internal links 3) title 4) meta description 5) keyword proximity and relevancy 6) bold and h1 tags off-page factors: 1) article submission 2) directory submission 3) social bookmarking 4) press releases 5) social networking these are the few factors that we consider but there are many more factors which we need to keep in mind while we do SEO. since you seem to be a beginner, therefore, you should first read some book or tutorial about SEO Thanks Shailendra
On Page Factors 1. keyword research 2. title and meta tags 3. alt tags 4. check broken links 5. site structure and navigation 6. h1 tags 7. sitemap.xml & robots.txt Off Page Factors 1. social bookmarking 2. article submissions 3. directory submissions 4. blog posting 5. press release above all are on page and off page factor which i use. i think so other people use this factor with extra some another factors also.
There are two categories of criteria that search engines use to rank pages: • On Page Factors - Analysis of the HTML source code for a page • Off Page Factors - Analysis of inbound links and the pages they link from
I would suggest you to refer this doc from Google; [pdf] http://www.google.com/webmasters/docs/search-engine-optimization-starter-guide.pdf