If you are looking for a workout buddy, try to find someone who is at least as fit as you. You want to be challenged during your workouts. Making sure the person with you can easily keep up with you will keep you motivated to continue to keep pushing yourself harder, especially if you are the competitive type.
My absolute FAVORITE exercise is walking my dog as we both work toward being thinner and healthier. I wasn't looking for a dog when I found him, but apparently Someone knew what would get me motivated to move. When I won't do it for myself, I WILL do it for Buddy! Anyone can do this, and any pace is okay, so those of us who are really heavy can feel successful from the get-go. I've lost 40, and Buddy's lost 3! YAY US!
Find a friend who is already exercising and join in with them to walk, join a gym, or swim. I would not have tried these activities on my own but now I have started, having a friend to exercise with is wonderful, but I no longer mind going on my own. It has only taken a matter of weeks ot get to the 'independent' stage
Make a plan to meet somebody at the gym at a certain time. Ask them not to tell you if they can't make it for some reason. This way, you HAVE to show up, because they could be counting on you, and there is less chance for you to back out if they do!