Accumulate flight experience per FAR 61.65:
The candidate must have at least 50 hours of cross-country flight time as pilot in command, which can include solo cross-country time as a student pilot. Each cross-country must have a landing at an airport that is at least a straight-line distance of more than 50 NM from the original departure point.
The candidate must make at least one cross-country flight that is performed under IFR and transits a distance of at least 250 NM along airways or ATC-directed routing and includes an instrument approach at each airport so that a total of three different kinds of instrument approaches are performed.
The candidate also needs a total of 40 hours of actual or simulated instrument time, including a minimum of 15 hours of instrument flight training from a Flight Instructor certified to teach the instrument rating (CFII)
Up to 20 hours of the instrument training may be accomplished in an approved flight simulator or flight training device if the training was provided by an authorized instructor. (CFI)
Within 60 days of the practical test, the candidate needs to log 3 hours of instrument training from a CFII in preparation for the test.
Receive and log training, as well as obtain a logbook endorsement from your CFII on the following areas of operation: preflight preparation, preflight procedures, air traffic control clearances and procedures, flight by reference to instruments, navigation systems, instrument approach procedures, emergency operations, and postflight procedures.
Successfully complete the instrument rating practical test (an oral and flight test), as specified in Practical Test Standards (PTS) for the instrument rating, which will be conducted by an FAA designated examiner.