How to find out minutes left on the Samsung M500?

Let me know which carrier you're with so I can tell how to check minutes left on your phone.

Does the Samsung M500 have call forwarding?

I checked the user manual and found no option for call forwarding. Although no setting has been found on the phone, you can still use the call forwarding feature depending on which carrier you're with.

How to save contacts to the SIM card?

Try this. Go to Contacts and choose an entry you want to save to your SIM card. From the options, choose copy/move to SIM card or something to that effect.