You should be aware that the visa application process is extremely lengthy. One person frequently posts here to say that he got his visa in a fairly short time (and that the US embassy didn't retain his passport during the application period) but I would still advise that you allow at least 5 months for the full application process (and not plan any foreign travel during much of that period). This is based upon the following:
(i) the police have up to 40 days to respond to your request for a copy of your criminal record. (You have to supply this to the US embassy. It will cost you a tenner) ;
(ii) the average waiting time to get an appointment at the US embassy is quoted, on their website, as about 2 weeks. (You pay $100 application fee plus another �10 for a courier to return your passport which, according to the website, is held at the US embassy while your application is under consideration) ;
(iii) the embassy website states that the minimum time before you'll hear the result of your application is '14 to 16 weeks'.
Further details of the application process are in my post here:
http://www.theanswerbank.co.uk/Travel/Question 289769.html
Chris