Eggshells provide calcium. Take the eggshells and crush them to a powder and you can dig this into the soil. If given the chance I would use sea shells too. They provide calcium in the same manner - just crush them well.
Coffee grounds fit the standards set by gardeners for compost materials. The grounds, when mixed with soil, release nutrients that make the ground richer and more acidic.
Plants that flourish in acidic soil will be healthier since they can get the needed nourishment from the ground. If you have a good supply of coffee grounds, just spread them evenly in your garden. Your plants will reward you by producing robust blooms.
Used coffee grounds + crushed dry egg shells = no blossom end rot