The preparation of the application and gathering all of the supporting documentation can take several months. Then, the request can be sent to the Immigration and Naturalization Service of the United States for review. The review process can take up to 12 months, so it is best to begin the application process far in advance of any possible future travel plans.
The application itself is, for all intents and purposes, the admission to the U.S. federal government that you have a criminal record. If your criminal record remains unknown to the INS and it is possible for you to obtain a Record Suspension prior to traveling, that would be the best possible solution, since the suspension would eliminate the possibility of your record appearing in a criminal search.
If the INS is aware of your criminal record, then including your record suspension in your application package will be helpful in getting your U.S. Entry Waiver approved.