My major rule was once you set your line, don't keep messing with it! I always gave it a few days for the critters to get used to it and scent to fade away. I had a buddy of mine that really had a hard time messing with the trap line. Needless to say he didn't catch alot of animals. I would set them where they could be observed from a ways off. Then check them every morning. I primarily trapped Racoons. That was in N. Central TX. A loong time ago.
