back when i had to study for uni exams I did this:
pomodoro with 50 mins of studying / 10 mins break (I read a study that said that after 1 hour it becomes harder and harder to pay attention to a subject without losing focus)
during the breaks I'd do some jogging, pushups, etc calisthenics because physical activity reduces stress, increases focus
if I was a bit tired I'd eat coffee (fuck boiling it, if you eat it you absorb 100% of it), I was too lazy to buy pills
piracetam, 4.8g every (biological half life duration) hours and before I'd take it I would eat food that is a source of choline: eggs, meat, dairy, etc
good nutrition, this is very important, to prevent mental fatigue and brain fog and short attention span and depression and anxiety and other shit
no distractions, repetitive, minimalist music (peter glass - glassworks as an example, or other electronic music)
clutter-free, comfy studying environment with good lighting
try to make as many mental connections as I can so that I can try to asymptotically reach the kolmogorov complexity of the quantity of information I need to memorize, basically I would try to do some shitty mental compression like ZIP, LZMA and etc do, I'd try to do shit like "oh so it's like this because of that and I can use X to describe Y and it also looks kinda similar to Z even though they're different"
and lastly, I know this may sound stupid, but I'd put some perfume on, I had anxiety when I was wearing that perfume because it meant that I had to go on and I hate that, because I had social anxiety, and wearing it at home would be some kind of CBT, i'd start to get used to it, also, smell is strongly related to memories, ever noticed how after sensing a familiar scent you start remembering all kinds of old memories? I wanted to make a mental association between the memories related to studying and the exams, so that at the exams when I was smelling the perfume I'd get a boost on remembering, like some sort of vidya buff