An easy way we got taught was to write down the number present for each of the elements on the side of the reactants and then do the same for the number on the side of the products. then you can see what needs multiplying and by how much!
My teacher used to write down everything he had to teach us, so if you have two of a product for example, write the formula again underneath instead of putting a 2 (just whilst you're working out, not on your final answer!), then you can see what you have and count them on the paper instead of in your head. And just keep doign leads of questions, eventually you'll gat the hang of it :)