Filing Google reconsideration request is the last resort for webmasters to recover their penalized sites. There are no guarantees it will help and hence plenty of rumors and speculations exist as to how it should be filed and what to expect.
1. Don’t rush to submit a reconsideration request – if you haven’t done anything wrong, you will recover your rankings within 0,5 – 2 months without any evident reason except that some time passed.
2. The whole process of filing a reconsideration request is described here: you will have to add your site to Google Webmaster tools (if you haven’t already).
3. “Full confession” helps: describe the situation in detail – everything that you suspect to have led to the penalty should be explained in detail. That might include past owner’s illegitimate actions, your own on-site optimization efforts, link building performed, etc.
4. Make sure your site is “crystal clear” at the time you are filing the request – everything that you might have done in violation of Google guidelines should be corrected.
5. Be patient – you are most unlikely to receive a response but, if everything is ok, you will see proper rankings within 1 – 4 months.