From my limited knowledge:

Meta tags
Linked to from other sites
Pay

If you look through the results it will probably already be there, just a long way down the list. If it isn't then you can submit it to Google. (Can't remember the page but you can just Google "Submit site to Google" or something like that.)

Meta tags give keywords and other bits of information that Google will utilise to give a more accurate result.

The more sites that link to you the higher up the list you will be (there are other methods too which I can't remember off the top of my head.)

You can also pay Google to give you a sponsored link. If there are many sites competing for the same keywords you may end up paying quite a lot. The link goes to the highest bidder but Google doesn't tell you what the current bid is. Anyone can come along, happen to pay more than you and you will lose your sponsored link.