I just got back to college so I'm starting to do weight training again for my muscles.
Oh nice! weightlifting can be a great form of exercise! 
Definitely, weight training is the best way to build muscle.
Do you switch between arm and leg days? 
When Im weight training I go between upper body muscles and lower body.
Do you use free weights or weight machines? 
Most of the time when I'm weight training I try to use the free weights but I use machines every so often.
Do you like to mix cardio in as well?
Weight training
Weight training is a common type of strength training for developing the strength and size of skeletal muscles. It utilizes the force of gravity in the form of weighted bars, dumbbells or weight stacks in order to oppose the force generated by muscle through concentric or eccentric contraction. Weight training uses a variety of specialized to target specific muscle groups and types of movement.
Sports where strength training is central are bodybuilding, weightlifting, powerlifting, strongman, highland games, hammer throw, shot put, discus throw, and
as Metabolic Resistance Training, actively seek temporary muscle failure; evidence to support this type of training is mixed at best. Irrespective of their program, however, most athletes engaged in high-intensity weight training will experience muscle failure during their regimens.
Beginners are advised to build up slowly to a weight training program. Untrained individuals may have some muscles that are comparatively stronger than others; nevertheless, an injury can result if (in a particular exercise) the primary muscle is stronger than its stabilizing muscles. Building up slowly