I doubt there is any 100% reliable way, or any way that works for everyone (cause people are different), so it's partly a case of finding out what works for you

I doubt there is any 100% reliable way, or any way that works for everyone (cause people are different), so it's partly a case of finding out what works for you. A useful discovery for me was that emotion is a greater driving force that rationality. Rather than making a list of all the reasons that exercise will be good for you, spend time visualising exactly how wonderful you will feel (in as much detail as possible) when you are fit, and spend time visualising how bad you will feel if you don't get fit. It might not work for you, but if it does it can be very powerful.