The first thing you should do on your journey to a lean, hard body is to exercise. Duh! That kind of goes without saying. Perhaps even prior to beginning an exercise program is the mental decision and preparation of committing to doing whatever it takes to get the body you want. Flip the switch. Decide and commit beforehand and you will be ready to start making your physique goals come true. You will not develop a hard body without resistance training, so start on a resistance training program for sure.
The last thing you should do to get a hardbody is to starve yourself! Starvation diets have never worked, will never work and are foolish to use at any point (if you are trying to build a hard body). A hard body means your muscles are full and tight against your skin. It is impossible to build a hard body without making sure your muscle are fed first and often. If you starve your muscles, they will atrophy leading to loose and saggy skin.
Your body will look exactly how you eat. A body fed properly and exercised properly with resistance training (first and foremost), will appear lean, fit and hard. A body deprived of proper nutrition will look depleted, sickly and will have loose skin. Most people who are on exercise programs want hard bodies. But many of those same people will not follow a proper nutrition plan that feeds their muscles because they have believed the lie that tons and tons of cardio and starvation leads to a fit lean body.
So the last thing to do when trying to develop your hard body is starve yourself. Feed your muscles, give your muscles resistance training and get plenty of rest and your body will respond nicely. Forget the "biggest loser" mentality of dieting and training. None of the best trainers implement those methods for their clients because they know the results are temporary.