Preparing for an MR scan is very easy. You can take all your normal medications and follow usual eating schedules unless your doctor gives you special instructions.
The only unusual preparation for an MR scan is that all removable metallic objects must be left outside the scanning room, including removable hearing aids, dentures and other prosthetic devices. Credit cards cannot be brought into the scanner room since the magnetic codes on them can be affected by the magnet.
For optimal image quality when performing head scans, all makeup must be removed since it may contain metallic powders which are magnetic and thus degrade image quality. You may be asked to wear a hospital gown, since clothes may have metallic fasteners or metallic fibers that can interfere with the imaging.