Rarely used for storing a car these days, garages are typically dumping grounds for things that you don’t have space for in the house. Sheds can be little better. So do a good declutter, try to organise tools or decorating equipment in labelled boxes ready for the move. Store what you can on shelves and walls. A buyer won’t expect it to be empty, but the more filled it is the more they’ll think your house doesn’t have much storage.
A potential buyer probably won’t look in your attic storage but start clearing your attic as soon as possible. It will take so much longer than you think. Reduce your moving stress, get ahead and start decluttering and sorting your attic now.