Getting your information straight from the 75th Regiment recruiters is your best bet, but this is what I know.
You need a packet that consists of the following,
Current and Updated ORB (your personel jacket)
Army photograph of your self (like your military ID)
Current PT score card (should be 90 points in each catagorey at minimum)
4187 stating requesting assignment to 75th Regiment, signed by your BRIGADE commander
Copies of all your AERs and OERs (evaluation reports)
Letter of intent on why you think you should be considered for Ranger service with contact info
Current AIRBORNE RANGER physical signed and approved by your PA and current full bloodwork
Also, being Airborne and Ranger qualified (as all combat arms officers should be anyways) will help you drastically in getting accepted.
God Speed there future Ranger......