back after couple years

[blahblah]

i use to lift and quit a couple years ago, and joined a gym and started back this week. Sitting here bored i thought i would do some research on lifting and now i'm confused. Back then everything i read said that the 1-5 reps for strength, 6-12 for muscle, 13+ for endurance was not true and you had to lift heavy to get big. So i always lifted in the 3-7 rep range and usally increased weight after getting to 7 reps and it usually put me down to 1-3 reps. Now everything i read is saying that the rep ranges are correct and lift 6-12 reps for muscle mass. Is this true or am i being mislead? Now i know people will say whatever works for you do it and if what i used to do worked then stick with it, but the thing is back then i never kept up with the calorie intake so i never grew cuz i wasn't getting enough calories, but now i'm starting back with keeping track of how many calories i eat a day. Just wondering what rep range i should aim for. Also say i need the 6-12 rep range to build muscle is this using a weight that all i can do is rep out 6-12 reps or a weight that i can prob get 15 reps but i stop at 12 reps instead?