Love yourself first- If you don't you will struggle to love someone else.
Love your own company- Enjoy the hobbies and interests you do alone and keep them up when you get with someone else- you still need to be able to enjoy 'me time'.
Be happy- If you are not happy- don't think that someone else will fill that void. Find what makes you happy and pursue it.
Talk- About money, kids, and religion- to name a few. Make sure that you agree or at least have a common ground on all of these points and if not entirely- make sure you can and are willing to make compromises.
Fight fairly- If you have an issue- work it out sooner rather than later or it will only grow in magnitude and become a much bigger problem.
Honesty- Tell your partner if they disappointed you- it may hurt at first but at least they know how you feel and likely won't do it again.
Respect- Choose your words wisely- you can never take them back- and people remember the worst things you say to them more than the best.
Be friends first- Start out with a solid foundation of a friendship and be sensitive to each other's needs and feelings. Trust each other and lean on each other when one of you can't do something on their own.
Accept their imperfections- No-one is perfect- so accept that they are a little rough around the edges and if the moment allows- laugh at them.
Do little things- Tell them you love them, pay them compliments, be spontaneous, close the door when you are in the toilet and give little gifts when they are least expected.
Don't stop having sex- If you are keeping track- then you need to have more sex. Reconnect with regular sex.
Want it- If you don't want to get married or have any doubts- then don't.