I have been married for 5 years and with hubby for 8 years.  Before I met him, I was in a serious relationship for 3 years.  Looking back now, I realized that I knew he was not "the one."  At the time, I just did not want to admit that I was wrong and wasted 3 years with a looser.  Now I understand that relationship taught me what not to do in this relationship/marriage.  The bad relationship has definitely helped me learn

1.  If you are mad at your spouse, wait until you can talk about the issue without yelling or screaming, but in a calm manor.  

2.  Pick your battles.  I am a clean organize person.  My husband was not.  I realized that I could sit in a spotless picture perfect house or I can learn to calm my anal cleaning habits down---and it helps that he getting better too.  So, after a few years, we met in the middle.

3.  No name calling, blaming, or swearing when we are discussing/talk about a problem.

4.  Do not bring up past fights.

5.  No attacking the others family. 

6.  Try to see the others' point of view or side.   

7.  Most important----treat your spouse the way you want to be treated!!   

And as far as knowing when it is true love----sorry, but I will say the same thing that I heard for years and years, and HATING hearing but now I know it is true----You will just know.  And like I always tell my brother----look for the red flags.  When it is the wrong person, there is always red flags.