math/physics-y stuff:

practise, practise, practise and then when you’re done practising, go practise some more. even if you are not the sharpest knife in the drawer, substantial practise can bring you impressive results.

history/theory/memorizing:

make it interactive. there is nothing in this world quite as boring as memorizing piles and piles of dry facts. use flash cards, make up jeopardy-like games, study in groups if you’re able to work constructively with people, butcher the book with highlighters and pencils (if you bought it. school books? no-no), associate boring facts with fun(ny) facts (e.g. global history exam is much more fun if you think of stalin as super mario and hitler as your quirky great-aunt mary who executed 6 milion ants in her back yard).

if you hate reading, make recordings of the material you need to know. or if you’re a visual learner, make sketches of what you’re studying.

hope it helps.