I'm trying to build muscle now that I've lost fat. I know to lift heavier with fewer amount of reps, but what do I eat, how much and what about shakes and supplements? Which foods help a lot and what are the foods that I should stay away from?
If its pure for muscle mass a rep range from 10 to 12 is proven to be the best.
For training i would suggest to you that you create or find a schedule which focusses on compounds. Those are exercises which work several musclegroups. The main compounds are squats, deadlifts and presses. This will help you to develop strenght next to mass and 'forces' you to move correctly.
As for eating, its important to eat atleast a lil more than you burn. These extra energy sources will be used by the body to build your muscles. Protein is the essential part in this. But extra carbs wont do you harm either. Just dont overdo it on the extra calories or the fat will come back faster than you like hehe.