Adding ingredients to your mix
When adding sultanas, nuts or other fruit to a mix, always drop them in the flour first and shake around. Coating these items in flour will ensure an even spread through the batter instead of clumping or sinking.
When using berries in your muffins, mix them with a few spoonfuls of the mixed dry ingredients before mixing in together. This coats the berries and prevents them from all sinking to the bottom of the muffin.