As far as i'm concerned you need to really look at your diet... if your trying to lose weight (or gain) you need to focus on your diet first and then a workout routine. If you don't have a diet in place there almost no point to going to the gym.
I would suggest planning out your meals, as in know what your going to eat a day in advance and how much. I follow a 30/40/30 ratio of protein/carbs/fat, but i'm trying to gain... once i get to the weight i want, i'll do a "cutting" phase and follow 40/30/30 ratio to loss the fat.
I'm kinda hard core you might say, cause i not only plan out what i'm gonna eat, but i use a program to make sure i stay exactly within that ratio. Ohhh and you also have to make sure your eating fewer calories than your body requires...(that's a given, but just keep it in mind)
As for foods, try and eat as many whole foods as possible, eggs, chicken, steak, oatmeal (plain), rice, any veggies or fruit, wheat bread... basically the more ingredients on the side of the box or packaging, the more processed and the less nutritional value. I've read that bleached flour is probably the worst thing you eat too (white bread).
It doesn't have to be this plain, but mac and chez probably wouldn't be my "ideal" carb source...
Moderation is the key.
I would make sure to do a little cardio in there, not just lifting... It doesn't matter what exercise you do, running, biking, elliptical, etc.. you just want your heart rate to be constant for 30-45 min @ ~75% of its max
But overall your diet is gonna determine if you lose that extra 20 lbs...