Global Link Popularity of Site
The overall link weight/authority as measured by links from any and all sites across the web (both link quality and quantity) The quality of linking sites, the proximity to important "seed sites", the number of thematically related links from other relevant sites, and ratios of one-way inbound links to other kinds of links are all important, and together can trump pages that are far more heavily linked.

Other aspects

• Make sure you host your nC server with a reliable hosting service, if you don't self-host. If the server is often inaccessible it can reduce your ranking.
• Don't have a lot of duplicated or very similar looking content, and don't duplicate meta-tags or page titles.
• Don't link out to low quality sites or obvious spammers.
• Be very cautious about participating in Link Schemes, or pay-for-link programs. These may violate Quality Standards and result in you being black-listed.

Adsense, Adwords and other commercial schemes

At the end of the day, you may find that advertizing will be necessary to get the traffic you want to your websites.
All nC sites will work very well with Google, Yahoo and other schemes.

You will find these free third-party resources useful:

Working with Google

Working with Pay-per-click