Recently I went to a conference and listened to a talk about this subject and here are the best ways to learn:
Look at the new word or rule, cover it and rewrite it.
Ask someone to test you.
2. Distributed Practice
This means revising a subject regularly, for example 10 minutes every day, this is better than 1 hour once a week.
3. Keywords & Mnemonic techniques
Invent your own phrase or way to remember, for example Roy Of York Gave Battle In Vain helps me remember the colours of the rainbow, Red, Yellow, Green, Blue, Indigo, Violet.
4. Interleaved practice
This means mixing subjects, for example revise English for 30 minutes, then French, then Maths… Instead of big blocks of one subject.
Highlighting key words and rereading were mentioned but these are not the best ways to learn.
So, try some of these and remember, regular learning is the key to success!