Best way to do exercise is to make it part of your daily routine. For example, if you drive a car, park it 30 minutes away from where you start work. Or, if you get the train the walk from the station to the place. Same with bus.
I have been going on a morning walk, on Mondays-Sundays for 3-4 years now without fail. About 45 minute walk. Not intense. I just made a promise to jah that I would never stop this, and I have never stopped since.
Everything is your choice, but if I were you, I wouldn't start doing insane amounts. Nor is it healthy. Do 30 mins-1 hour a day. Having an active profession is much better, like gardening.
Exericse is just one part of our life in zion that is absent in babylon.
By the sounds of it, when you said that you smoked cigarettes and drank soft drinks. Sounds like your body needs a very good cleanse. I would recommend fruits and vegetables for this job.
It is very important that you know that the state of mind that you have expressed on these things (soft drinks ect) about liking them too much and finding it a chore to get off them is because they DESIGN them as drugs for the body; as poisons that get you hooked. It is important that you know that once you are off those things altogether, for an extended period of time, then you no longer crave those things, and actually find them quite disgusting.
I can say this from personal experience, because now I actually find those things disgusting and THOUROUGHLY enjoy ital food. You need to know that your taste buds have been indoctrinated, and that once you begin to de-indoctrinate them things will get easier, until you actively enjoy the right things.
Whenever I think of anything, I think how would this differ from the life in zion? And in the case of exercise, it is the case that it would be part of the daily routine, that you do imperitavely, to perform each action.
I would start slowly with cleanses; fruit and vegetable juices are excellent.
I hope this helps,
All the best,