I never try to get my man to go on the diet with me, but I let him know I'm trying to lose weight and he is then less likely to suggest dessert if I don't, which helps.
The first 20 pounds I lost was because my sister had about 150 to lose. She lives far away and she was on the verge of starting weight watchers but didn't want to do it alone. I asked her if it would be easier if I did it with her, and we did in online but long distance. She's lost 150 pounds!
I've kept off the 20, and now I'm going for 20 more. It was a big help to talk to her on the phone and to see the changes in both of us when we got together.