Submit a sitemap using Google Webmaster Tools and make sure that your site is fully available and works well. You should see Google fetching your site almost right away (it actually may be a day or two or three) and it should begin showing up within the index fairly quickly.
However, it will be treated as if it were a relatively new site. It is all about trust. While you may be trust worthy (I will vouch for you- who do I call?), trust for a site goes deeper than that. Any site that has technical issues for a while takes a bit of a significant trust hit.
Google thinks, "Can I trust presenting SERP links to a site that has been offline for so long?" Remember, its all about user satisfaction for Google users more than anything.
Since trust is a foundation set of metrics, it will take time for your site to be fully trusted again. For this reason, Google will present your site in the SERPs rather cautiously and it will take some time to gain in the ranks. As an example, I had a 1 week outage in Aug/Sept time frame and I have only just recovered just over half of my search web traffic. This with fairly significant PageRank, site age, and excellent speed and reliability history for 14/15 years.
Remember that search engines are rather slow. But do know that Google will fetch and index your site rather quickly, it just may not perform as you would like for a while. But focus on trust issues and creating a kick-*** site and you will be fine.