30 mins of weight lifting help!

definitely do compound exercises --- they work several muscles at once to save time. a lot of people do 5 sets of 5 reps with their 5 rep max weight so that you get the definition quicker and are working as hard as you can. this is the most effective thing I have ever done for a workout and I see results instantly. one program you could look into is strong lifts 5x5. some exercises: pushups, pullups/chinups (could use an assisting machine if your gym has it), overhead press, bench press, dumbbell flys, squats/one legged squats and calf raises, deadlifts/one legged deadlifts and lunges/step back lunges with bicep curls. I break it up arms and abs/legs and butt and do each 2-3x a week. Core exercises I mainly got from P90X ab ripper x (amazing!) -- planks, lay on your back and put 1 leg perpendicular to the floor the other parallel to the floor but not touching and switch - SLOWLY!, knee ins and outs, laying down with legs slightly spead reach 1 arm up and over to touch the opposite toe, laying down legs vertical and arms extended behind head pull weight/medicine ball over head and up to reach toes, laying down lift both legs up perpendicular and back down to almost touch the ground, medicine ball side to side, bicycle, among some others. For those I usually do 24 reps slowly and for the twist and bicycle 50 reps. P.S. most of these can be done with either a barbell or dumbbells so they can be done at home or the gym if you have the right weights. And don't forget to increase the weight so you are always using your 5 rep max weight!