To check your application status. go to www.uscis.gov
http://www.uscis.gov/portal/site/uscis
On the left side of the page there is going to be a Case Status box. You will then need to enter your receipt number into that box and either hit enter on your keyboard or hit the check status bottom.
If your case is in their system then it should show up and tell you where your application is at. if it's not, you would wait and try again the following day.
Hope this helps. Post questions below.