Reps determine heavy or light, not weight. 

People hear that if they lift light weight and high reps, then they will get tone and not put on bulk.  So, they use very light weight and do easy sets of 20 or more reps.  And never get results!  That’s because they aren’t working hard.  If you want to see a specific type of result (tone), then you have to work hard.  To tone your body, pick a higher rep range, like 15.  Lift as heavy as you can 15 times.  If you can get 25 reps, then it is way too light.  If you can only get 4 reps, then it is too heavy.  The amount of times you can lift it determines if it is heavy or not, not the actual weight.  Remember, weight is just a number!

Make exercise a habit.  A week on and a week off or a month on and a month or two off will not cut it.  If you really want to see results and become a healthier person, you have to make exercise a part of your life.  You don't have to work out till you drop everyday, but you do have to exercise consistently on a daily basis.