Positive of On Page and Off Page Factors

On Page Factors

Keyword in Tile Tag
Keyword in Heading tags, H1, H2 and H3
Keyword in Links
Keyword Image File Names
Keyword URL
Keyword in Alt tags
Keyword Prominence
Keyword Density
Keyword Frequency

Off Page Factors

Directory Submissions:
2000's of free directories are available. Choose among the best because some of the directories using "No Follow" Tags.

Search Engines Submissions:
Submit your sites properly. Do not submit repeatedly to search engines.

Forums:
participate in your industry related forums & discussion boards.

Blogging:
Create different blogs and write your own content. Participating in comments.

Press Release:
you can post Press Release, which also works like article junctions & directories.

Articles:
Write keyword & content rich articles on your company's updates, product release etc, and also inbound links.

Classifieds:
you can see some websites displaying free classifieds.

Social Bookmarking:
Social book marking it serve two purposes: it gets you incoming links and it popularizes your websites in your community.

Negative Factors:

Too much keyword repetition i.e.Keyword Stuffing

Invisible Content via text same color as background or CSS or other such methods

Doorway Page pages that are specifically written for search engines.

Duplicate Content Watch out for those duplicate filters.

Participating in Links Farms or services that try to artificially increase your links by doing shortcuts.

Cloaking showing a pages to search engines different then users see based on their IP address.