Advice for an exercise newbie?

Hi. I've been trying to lose weight for about a year now, but I've never fully dedicated myself to it. I always fall "off the wagon" and wind up feeling terrible about myself. I've decided to try really hard and stay focused on my weight loss goals, which I know means counting calories and exercising. The only problem is that I've never exercised before... I've walked on the treadmill a few times and done some workouts I saw in magazines, but I've never routinely worked out. I feel really overwhelmed and I don't know where to start. Does anyone have an exercise routine/exercise tips for a complete newbie? Thank you so much!