Step #1 is get a twitter account and follow Andrew W.K. This guy...I can't even describe really. Just trust me.
A few personal tips. Starting with: be realistic. Don't expect things to happen overnight. It's easy to not exercise and eat junk food. It's hard to exercise and eat healthy. Life isn't meant to be easy. It's mean to be challenging. Take a look at the consequences to each. When you take that easy path, how do you feel? You don't feel good or proud about that easy path, do you? However, when you go to bed at night after a day of the difficult path, when you spent the day exercising & ate well, you feel good about that discipline. And use that when you wake up, to keep it going. It's going to take weeks, months, and even years, but-you WILL get there. If...you keep challenging yourself.
However-engulfing yourself in nothing BUT discipline isn't good either. The key is balance. Being able to push yourself to do the things like working out, routinely, but also take a break. After all, you earned that break!
I'll throw in one last HUGE motivating factor for somebody like myself: music. Get yourself ready. Fire up your iPod. Or whatever you use. Throw on something you enjoy. And let it move you. Literally. If you really, really are into any type of music, your body will move to it. It's awesome.
https://www.youtube.com/watch?v=eByBvUms_tQ Music like this is very powerful, and has very motivating lyrics. Where they say, and you can say with them "I will, never give up. I will, never take the easy way out."