Direct Application of Coffee Grounds
Coffee grounds are an excellent free source of nitrogen, an element all plants need. A common misconception about coffee grounds as a fertilizer is that it may cause problems because of high acidity. But coffee grounds are close to neutral, with a pH between 6.5 and 6.8, making them a good choice for all plants. Each type of plant will prefer a different amount of coffee, so start small by adding 1 tablespoon of coffee grounds around each plant, lightly working it into the soil once a week. Observe how your plants react and add more each week until they stop showing signs of improvement.
Composted Coffee Grounds
Composted coffee grounds are probably the best, as they provide a good source of nitrogen and mildly acidic soil. However, if you don't want to get involved in composting, I think you'll be fine putting coffee grounds directly in the soil and mixing it slightly. It probably might take a little longer to break down on its own, but it'll be ok. Coffee "tea" is also one way of doing it, but I think it's more of a diluted one-time fertilizer drink for the plant.
Eggshells are rich calcium. Without the proper amount of calcium in the soil, plants may produce deformed blooms. You may be buying lime to prevent this problem, but eggshells are just as effective. Store eggshells in a large container of water, adding more shells as you go. Let the mixture steep for at least a few days or up to several weeks. Combine 1 cup eggshell tea to 1 gallon of water and thoroughly water plants. Up to 1 gallon of the mixture can be used per plant. The added calcium will give plants a much-needed boost through production season.
Powdered eggshells can be added around the base of plants as a slow-release fertilizer. This process will benefit plants all season, and you can add it throughout the growing season. Allow eggshells to dry, then pulse in a blender until they become a fine powder. Sprinkle around the base of each plant.