Need basic help with drop down or multi-selection

Need basic help with drop down or multi-selection

Let me start by saying I have zero experience here but I am a learning as I go. I have a small issue I am sure one of you can help with. 

In simple terms I want to ask customers how they prefer to be contacted. The options are Mail, Email, SMS, and Do Not Contact Me. I want to have a box appear for Email if they chose email as a preferred contact method and then also have box appear for Cell phone if they chose SMS as a preferred contact method. The address is required and we collect it earlier on the form so no need to include any instructions if they chose Mail.  I would prefer they be able to chose multiple but if not possible I am okay with them only choosing one. 

I have a field for "Preferred Contact Method" with the options of Mail, Email, SMS, and Do Not Contact Me. I have also set up the fields "Email" and "Cell Phone Number" and they are set to hide on load. I just can not figure out the script to have the fields show based on the appropriate response to "Preferred Contact Method".

Thanks in advance!