Pre-Med major here but have an interest in fitness & Health & sports training.
Anyway the bottom line is you have to be consistant, set aside an hour a day for this (think of it as an investment) 90 minutes would be better, but you can do it in 30 if you have to.
Here are some basics, for every pound of muscle that you add you will burn an additional 50 calories a day. So if you can add 5 pounds of muscle, just the additional caloric burn will cause you to lose 2 pounds every month (assuming wht loss is your goal). If you have not done any weight training you will gain 5 pounds in no time if you lift consistently. For this reason weight training is superior to cardio as cardio only elevates your metabolism during the activity and for a short time afterward, resistance training will create the hungriest cells that you possess & will be active 24/7.
OK so Here is a good work out:
Mon & Th Chest/tri/legs/back
Tue & Fr Shoulders/bis/legs
Wed & Sat Hard cardio( min of 30 min increasing to 60 min) on stairstepper
Mon & Fri Start with legs (mon squats/Fri leg presses)
Tue & Th Start with easy cardio (20 min on stair master) then whts
Dont look at this as a chore, look forward to it everyday rain or shine! Find a variety of excersises that fit into the above routines then change them up every 8-10 weeks with 1 one week off (from whts/do light cardio) in between. Alternate also low reps/heavy wht for strenght high reps/low wht for endurance. For example strenght 3 sets of 6-10 reps/endurance 4 sets of 12 reps with 30 seconds between. Mix in a highbred/ 4 sets at 15/12/10/8 reps. By May you will be ripped assuming you control your carb intake!
If you really want to go hard core do a wrestling/navy seal routine where you work out lots of cardio lots of high reps/low weights twice a day, U'll be ripped in 8 weeks!