Trust factors

1. A bunch of ranking factors that you only have a limited control of. Each of such factors does not add a value directly to the rank of a website. Instead, they increase itstrust rating. Google (and other search engines too) prefers trusted websites and gives a boost to their ranking. Trust factors include:
   1. Domain name age. Old websites seem more trustworthy than others. If the domain didn't change its owner - it gets even more trust points (though don't ask how many).
   2. The number and quality of inbound links, the PageRank. If many other websites link to this one - it is considered trustworthy. The quality of links doesn't play a significant role though, since you cannot be responsible for the links pointing to your website as you got no any control on that. Otherwise it would be possible to hurt your competitors by posting links to them from some malware sites.
   3. Website content. If a website uses pop-ups, pop-unders or some of the blackhat SEO methods - its trust rating gets lower.
   4. Outbound links. If a website links to other trustworthy sites it gets a boost to its own trust rating.
   I believe there are more, but these ones are the most important.
   
2. Press releases, related resources, word of mouth etc.
   That's a bit off SEO theme, but still can help to obtain a couple of links. You have some exclusive info? Share it with the community on some thematic resource. Do you have some astonishing news in your industry? Tell the world about it with a press release. Are you running a special promo action or offering a discount coupon? Let others know about it.
   
   All of these usually doesn't require a single cent from you. You can send a press release via Pr Web, you can register on some forums within your industry for free to share your thoughts, you can tell others of your promo coupons at Giveaway of the Day or Retail Me Not and other similar sites. Don't neglect the power of word of mouth!