From a mom whose son married last year and has a daughter getting married in June...I would give the following advice:
1) I think one needs to THINK seriously before getting married. If there is something about your future spouse that you think you will 'change' after you are married...then, don't get married. Going into a marriage with an expectation that you will 'change' the guy's attitudes, quirks, or faults is a recipe for disaster.
2) No matter whether both are earning an income...each person needs to have some money to do with as they please. DH and I have our joint accounts but we each also have a personal account with a debit card at different credit unions. My quilting and fun money comes from what I have put in that account from my bi-weekly paychecks via direct deposit.
3) Don't gripe about each other behind your backs (with friends/coworkers).
4) Have some hobbies...and don't rely soley on your spouse to do things for you that you could do yourself. Retain your individuality.