Measuring cups play a very important part in cooking or baking. It is important to understand that different ingredients have different weights.
For example, a 250ml cup of honey will weigh 340g.
For dry ingredients, scoop them into the cup - ensure it's overflowing. Then use the back of a knife and scrape the excess ingredient off. Don't be tempted to shake the cup as you don't want to compact the ingredients.
For wet ingredients just fill to the top of the cup.
But look at the recipe you are using, American cups are 240ml while UK/Australian cups are 250ml. Start your own accurate measurements by weighing your ingredients and writing down the measurements in grams next to the cup measurement in your recipe book.