I hate to exercise, so what motivates me is to walk with a purpose in mind. For example: a walk to the corner store to pick up fruits, armed with my back pack to carry my purchases = 40 mins round trip. Beats walking on the treadmill anytime!
I've spent too much money on gym memberships already. I always have an excuse not to go: too tired, it's cold outside, have a headache, and so on. I even got myself a gym buddy but she too was discouraged. So now I walk any time I can. I even got myself a pedometer. Counting my steps really helps.