In simple terms (for me, at least). Start small, but make sure you're consistent. At the start of the year, don't stress too much if you're not doing 2+ hours a night or if you're not revising x subject every night, the biggest thing you need to do is a get a routine started. Doing all your homework is a good start, and then consider reserving 30 minutes or so just to do a little bit of revision, or maybe to read ahead. The big thing is that you're doing this at least every weekday, and as you find yourself regularly doing 30 minutes without needing to time yourself/actively push yourself into doing it, you can consider increasing the time to an hour, and so on.
A big mistake I used to see with people around me is that they'd go "right, i'm going to do two hours every night!" without any previous habits or motivation to do so. It works really well for about three days, and then they burn out and feel rubbish for not doing anything. It'd be like going out for a run without any prior running experience and trying to sprint 5k through unmarked woodland at night. It'll go badly, you need to work up to it.