Honestly, the place I usually tell people to start is with making a budget. Suggesting people cut back on eating out, getting fat and buying fancy coffee ice cream diabetes bombs is a great suggestion, but tends to fall on deaf ears as long as people don't realize they're spending hundreds of dollars a month on those things.
I didn't realize I was eating $150/mo++ of fast food till I signed up with Personal Capital and started tracking it. Then I was like, holy shit! I'd never pay for cable or a car payment, why am I spending hundreds of dollars on pizza, chicken sandwiches and hamburgers?!
Step two is to tell them that saving 50% of their income means they can retire in 15 years, and that saving 75% of it means they can retire in closer to seven.
Then, after that, comes the advice on what to cut back and how. Knowing your spending, and knowing what is possible (retire 7-10 years from now!), sets the stage for the rest. For someone really interested in retiring sooner over other priorities, like hamburgers and having stuff, it should come naturally.
IMO, anyways. :)