I fluctuate between my ideal weight and 20 lbs over. If my clothes are feeling tight, big clue to stop slacking and get to work. For me also, if I don't like what I see in the mirror, it's a huge blow to my self esteem.
What helps me the most is to try for 2-3 x per week of cardio (which for me is hiking in the mountains outside my door), and, more importantly, lifting weights twice per week. I am a petite girl for the most part, so I use wimpy 10 lb weights, and use a dvd for a guide. Recommended to me by a friend, the one I have been using lately is called "the abs diet 2 workout". It goes through a series of squats, lunges, arms etc excercises and I find the visual guidance really helpful. A whey protein shake before and after the weights is part of my routine.
Pilates is also really helpful for core muscle strength and to prevent back pain at work for those who are standing all day. (My real job is as a nurse, and I am on my feet for 12 hour shifts). Again, I hate the gym, and I use a dvd. I like anything by the Giam company (not cheesey, often filmed outdoors, nice new agey music), and my favorite instructor is a Giam instructor named Ana Caban, you can check her dvd's and reviews at Amazon. Pilates will change your entire posture and the way you carry yourself, and I think helps prevent back injuries at work.
I've been slacking lately and feel awful about it, and have just started up again my routine 2 weeks ago, after a lapse. Already I am looking and feeling better.