I'll advocate for: see a marriage counselor regularly! Before getting married if possible, and at least every couple of years after. Many people take more seriously the maintenance of their car than the maintenance of their marriage.

There's nothing magic about what you'll learn, and a lot seems pretty elementary. But go before you have a problem! This is one of the best things my partner and I have done. We know that if we have an issue there's someone we can talk to for help, and because we go regularly there's no stigma with going.