Egg cartons are the perfect shape to store most of your condiments, especially if they are running low and need to be flipped upside down.
Use a lazy susan
Food stored at the back of the fridge is easy to forget about. Place a Lazy Susan on the shelf and improve access to all your fridge items.
Hang bags with bulldog clips
If you have wire shelves, use bulldog clips to seal and hang half empty salad bags or cheese.