Friend,
There are few simple way,
1. Your Attorney call to 800# customer support (printed on ur receipt and online)
2. Your Attorney send a request letter to the Service center where your 485 is pending.
3. You also can call to 800# customer support and inquire about your case status.
4. You also can send letter to service center, but the best thing is always use/ask your attorney to do so atleast sending letter, becz it does make difference you send inquery or ur attorney sends.
Good Luck