Tapping the power is dependent on individual effort. Crystals have their uses, but are not everything that some promoters claim. They are not the ultimate answer to all of humanity's needs, and will not replace individual efforts to improve the person's life. Crystals can be a lot of fun. They will not solve all your problems or magickally make you rich, successful and loved.
Common sense is the best guide to their use.
Other things also have their special attributions. For instance, candle colors are believed to have a special significance. So does incense, scents, metals and herbs. This guide lists some of the more common items and their special significance. It can help you select those magickal things you need.