Kara is really giving you a goldmine of advice. What I would add is that you should try to shy away from just working certain muscles, or body parts at the expense of others. The last thing you want to do is train one body part too much without working its associated antagonist. All that'll do is lead to muscular imbalances, and ultimately, injury.
So for example, let's say that you want to firm up your quads so you work the squats. You must also work the antagonist muscles of the hamstrings in order for your body to remain balanced.
A balanced approach to weight training is the key to the body you're after. So, make sure to work the 5 main muscle groups of the body equally as hard. Those are the shoulder girdle (chest and shoulders), the upper back, the quads, and the rear chain (calves, hamstrings, glutes, lower back), and the core. Use compound exercises that Kara has prescribed.