Finally gonna commit

I was placed on a diet a couple weeks ago and I managed to lose 8lbs.I gained it back but knowing it's possible to do so gave me more initiative to try and commit.Currently i'm(19m 5'2) 148lbs and want to get down to 120lbs.I'm gonna try and cut out the junk and go back to drinking only water.Exercise more (which isn't hard since i don't at all) and eat a little less.Any tips or advice on how to lose weight is appreciated!