Welcome to the forums, Amber! Regarding your skin, Mike's right, it has a lot to do with elasticity, but I think as long as you lose the weight naturally (i.e. not through surgery) you won't have any significant problems with loose skin... at our age (I'm 24) the body tends to adapt to its conditions really well so as you lose weight your skin will automatically start to tighten up. If you lose really fast it might feel "less tight" but the longer you spend at a given weight the less that feeling will linger.
1) eat real food - more vegetables, moderate meat, moderate fruits, less grains, less sugar, less vegetable oils.
2) exercise - moderate intensity cardio, sprinting, heavy lifting, dedicated stretching and mobility.
3) live - relax, de-stress, meditate.
Disclaimer: I'm not professionally qualified to make any formal recommendations. I've just done my homework and I'm my own guinea pig. All of my data, unless otherwise cited, comes from a sample size of n=1 (me).