One of the core strategies to get a high ranking on Google and Bing is to get inbound links from other sites.
This is nice little primer from James Nicholson of Rocket Marketing in how to achieve this.
As in other areas, the search engines are keen to reward links from good, on-topic websites.
The most important thing when it comes to receiving links is relevancy. You want to make sure that you are being placed on sites that are relevant to you and what you offer, so think about what the other site does or offers before you make a request. Relevancy is one of the biggest factors when it comes to search engine algorithms and this is increasingly the case. It is also fair to say that the more relevant your site is to the original site, the more likely it will be that your request for a link will be accepted.