1. Don’t taunt your mate. Avoid the temptation to do or say those things that you know irritate your mate. This includes constant teasing, ridicule, and gestures that send your mate into a tizzy or rage. Also, avoid the body-language "comments" ranging from rolling your eyes to smirking sarcastically.
2. Change the subject. If it appears you’re going down that familiar trail of bickering, ambush the conversation by jumping in with a comment on a more pleasant topic.
3. Keep to your agreements. If you say you will be on time or pick up your dirty socks, then do it. Flaking on a small agreement can escalate into something bigger. Making agreements and not keeping them — minor or major — can set the stage for constant arguing, and no couple needs that.
4. Hold your tongue. Though you may want to blurt out a criticism or a snide remark, restrain yourself. When you decide to keep some remarks to yourself, you may avoid petty arguments altogether. Remember that old adage: "If you can’t say anything nice…"
5. Don’t engage. Another famous saying: "It takes two to tango." If you refuse to play the bickering game when your mate starts in, he/she will have to look elsewhere to direct his/her jabs.
6. Forget about being right. It is oh-so tempting to want to climb all over your mate when he/she does not live up to his/her minor promises (like not getting your car washed yesterday when he/she promised). Yes, you’re right: He/she is wrong, but is it worth getting into a huff about? Granted, it’s irritating to count on someone for something and not have them come through, but save the "I’m right and you’re wrong" for the big stuff, like when your mate says he/she will make a commitment to stop swearing in front of your parents and continues to do so.
7. Forget the "tit for tat." It’s a natural response to want to get even with those who hurt your feelings or make you mad, but what does that do for your relationship? When the sun sets, wouldn’t you rather snuggle up and watch it together than sulk in different rooms? There is never any point in leveling the playing field.
8. If it’s not a deal-breaker, let it go. Sometimes all of us get mired in the petty things, when it is far better to roll with them. As you begin to partake in a petty argument, ask yourself whether what you’re fighting over is something that could cause the demise of your relationship. If the answer is "no," then go with the flow.
9. Find another outlet for venting. Many petty arguments are a result of one person unloading on another because he/she has had a bad day. Take up boxing, swing that racket extra hard on the tennis court, get on the treadmill, run like Forrest Gump, but do not take out your bad day on your mate by picking a fight over nothing. Direct your frustration elsewhere.
10. Be prepared. If your mate gets lost every time he/she gets behind the wheel, find your destination in Yahoo! Local ahead of time. When your mate starts to complain that he/she cannot find the way, don’t nag. Slide the directions over to your mate or read them off nicely.
11. Ply your sense of humor. Nothing diffuses a petty argument faster than humor. Make light of the pettiness; you will find the absurdity of what you’re fighting over amusing. Humor is essential in any relationship.
Source; http://dating.personals.yahoo.com/singles/relationships/