I made the decision to get healthy about 3 months ago, and I've never felt so good in my life. It's all about routine IMO.
Once you start eating healthy (the tips that have been mentioned are exactly what i've done), you'll want to eat healthy. The thought of any fast food now is really gross.
The exercise routine is hard to get into, but after a week or 2 you'll feel like you need to get to the gym or the running track...then you're off and running. pun intended.
The third aspect of the routine, and the most important is sleep. Getting enough sleep gives you the energy to do the above 2 things properly.
A lot of good info at
www.menshealth.com