Format doesnt matter, you can always convert,
Most ringtones will copy from the card to the phone when used as ringtones.

I am planning on buying a Samsung M520 cell phone and have a question... In the past I have made my personalized rings tones for my Motorola cell phone and loaded them using a plug/USB cable from my PC. The M520 has a Micro SD memory Card in it and I am wondering if I can transfer the personalized ring tones in my PC (in any format to the SD memory card) and they will work... If so, what format do they need to be in? Would like this info before I make the purchase.. Thank you