best way to address envelopes?

What is the correct or best wording when addressing the envelopes for a married couple?

Mr. and Mrs. John Smith?
Mr and Mrs Joan and John Smith?
or Mr. and Mrs. Smith?

im sooo bad at this!

how about for a none married couple?

Ms. jones and Mr. Smith?
Mr. Betsy Jones and Mr. John Smith?

thank you!!!

I did...

for a married couple:
Mr. and Mrs. John Smith

for a non married couple:
Mr. Betsy Jones and Mr. John Smith

we did outer envelopes: mr and mrs smith
inner envelopes: mrs and mrs john smith