You've received a lot of good advice from the trenches, above. Whatever you choose will depend very much on you, your children, and your family system. I'm just going to add that, no matter what strategy you end up using, stick with it for a little bit before deciding that it is ineffective. Children commonly will up the ante when you implement a new strategy. An initial escalation in undesirable behavior may be a test to see if you really mean it. (Whether it's limit-setting, or expressions of unconditional love and affection.) Almost any mediocre approach, consistently applied, will be more effective than the most fabulous technique employed weakly. Don't feel defeated if it seems to get worse before it gets better!
