Study in a different space to where you spend your time relaxing/sleeping. This helped me so much. Warm drink - light music in the background, a heater nearby so you're comfortable. Plan out your revision before you do it, this can make it 10x more efficient. Take brakes for example some of the popular methods are 40 mins work, 20 mins break but it's highly dependant on how you yourself work best. Others do 2 hours work 1 hour rest etc.
Depending on your subjects, for science subjects Biology - Biology Carol for A-Level (her course costs £50 for both years but she goes in detail and goes through exam questions at the end which is the best way for revising biology especially).
For Chemistry A Level- Elliot Rintoul on Youtube, his videos he goes through exam questions and explains things really well.
For Physics I dont know but Im sure there are resources.
Overall, for science A-levels please focus on EXAM Questions, the grade boundaries are high and not only do you need to know a huge amount of content, but they are very specific with the terminlogy which you will only know through doing bulk exam questions.
For GCSE Sciences (as I dont know which you are currently doing) freesciencelessons on Youtube is literally undisputed. I got 9/8/7 Bio Physics Chem and I barely did much work except his videos.
Hope you do well