I couldn't get up steps without huffin' and puffin, so I started in.
Some suggestions: Find a good lookin personal trainer, and sign up for a couple sessions. If its your first time in the gym, you do NOT know what to do. If you imitate-- you won't be doing the motions properly, you won't make the kind of progress you want, and your interest will fizzle and fade.
Motivation for me was 100% seeing results. I worked with a trainer once a week, and by the end of two months I had put on a lot of nice muscle here and there and dropped over 15 pounds, without heavy diet modification. This is after a full year of going to the gym and knocking weights around like a moron. Cut out the intensive carbohydrate loading and use low calorie protein shakes to curb hunger and assist in the development of lean muscle.
Finally, 5 days a week: 30 min muscle group \ 30 min cardio three days a week, and full hour cardio on the off days. Do legs on the last day before the two day rest.
For full cardio days, i recommend doing a spin class or something of that nature-- just pushing along on a treadmill or elliptical like all the other dummies will not assist in keeping yourself motivated. Spin is serious business.
One of the top mistakes people make is to go in and do either 100% muscle or 100% cardio. For building lean muscle and looking better, you want some of both. I know iron man super strength guys don't do cardio, but they look gross, as well.