While I certainly don't have all the answers regarding marriage, Dan and I made it past the newlywed year with our marriage (and our sanity) well intact.
Don't ignore problems. The newlywed year sets a precedent for the rest of the marriage. That's not to say if you have some problems your first year that you are doomed to repeat them throughout your marriage, after all, just like anything else new, there is a learning curve in marriage. However, you do need to take issues seriously from the get-go and address them as they come up. Don't assume that things will magically get better as the marriage goes on; it won't. If something bothers you now, it will still bother you in twenty years and your spouse will never know it bothers you if you never let him know. Be quick to forgive, but don't move on until the issues have been addressed.
Set boundaries. The first year isn't just key for how you treat one another, it's also lays the groundwork for how you relate with each other's families. If you have problems with an in-law, this is the perfect time to discuss boundaries with your spouse and enforce them from the get-go. Many newlyweds expect that many of the issues with in-laws that were evident while dating will change now that you are married. After all, now you and your spouse are your own family and there is some separation from your family of origin. Unfortunately, not all in-laws see it that way. It's best to address those issues before children complicate these problems even more. Make sure you are honest with yourself about how your own parents treat your spouse and marriage, as well.
Don't air your dirty laundry. As a woman, it's sometimes tempting to disparage my husband to my friends. It seems that we live in a guy-bashing society, where female friends seem to one-up each other on the whose significant other said/did/wore the stupidest thing. Before you open your mouth to join in, think of how your husband would feel if he overheard you saying such things (and simply for the purpose of making your friends laugh at him). If you are having a serious fight or problem, you can confide in one close friend if you are doing it because you are sincerely looking for help or advice, but make sure you fairly portray both sides of the situation. And for goodness sakes, even if your mom or dad is your best friend, do not put your spouse down when you speak to them. I know this can be difficult because I tell my mom everything, but it really is key in a good marriage. Most likely your parents already are on your side and you don't want to give them reasons to dislike your spouse! (The alternative isn't fun either. My parents think my husband is amazing - and he is! - but they side with him on everything. It's not fun to get a lecture from your parents for being mean to your husband, even when you know you are right!)
Have fun. Newlywed life only lasts a short time, so enjoy it while you can! Don't get so caught up in planning for the future that you don't enjoy the present together. Once (if) you have children, it will be many years before you will again be able to spend so much alone time together and be spontaneous. Use this time to create memories that will be a strong basis for your life together. I was recently reminiscing about our travels and am grateful that we took advantage when we could, before we were tied down to responsibilities