How do you get a lot of studs on Lego Harry Potter Years 1-4?

Answer 1

The best thing you can probably do is buy the multipliers from the shop, which will multiply your studs you get per level by how many multiplier you turn on.

The more multipliers you turn on the larger the multiplier gets.

Answer 2

You can cast spells on every object that you can and collect all the studs that come out of it before they disappear.