Stop learning when it is no longer fun.
Take regular 20-30 minute breaks.
Study in a dedicated room, not in your living room or bedroom.
Use mnemonics to memorise facts.
Try to understand concepts rather than memorise.
Also learn in groups with motivating people.
Don’t mark randomly, take notes as you learn.
Explain to others what you have learnt so that you understand it better yourself.
Sleep 7-8 hours a day to anchor what you have learnt in your long-term memory.