I agree with communication and putting each others feelings first. My husband was single, like single single, for 40 years of his life - when we were dating he would put his friends wishes and wants sometimes before mine. Being married for one year I have noticed a huge difference in him & how he approaches and plans things.
The importance of counseling, communication, combining of finances not just talking about it, quality time, how to fight ( arguments, discussions, uncomfortable topics, not physically)....Let's just say that year one was definitely a hard one and we both had a lot to learn despite knowing each other as friends for 15 years, and dating for 5, and engaged for 2.5. Life also happened which threw a lot of curves which we didn't expect.
Year one of marriage was definitely a hard year, but we made it through and are halfway through year 2 and it's been much better.
I'm learning how to hold back my every thought (lol) and he is learning to tell me more when he is mulling something over. Communication is key, and it's important to listen to your spouse and his/her concerns about every situation.