For a crystal to be your own, it needs to be programmed. This will attune its energies to your own frequencies and desires. Before you program your crystal it is usual to dedicate its energies to the highest good of all.

Dedicating Your Crystal
You can dedicate your crystal immediately after receiving it and after it has been cleansed. Dedication is simple, but it will make an enormous difference to how effective the crystal will be. Dedication focuses the intention that the crystal will be used positively for the highest good of all concerned.
Hold the crystal in your hand, picture light surrounding it, and state clearly that the crystal will only be used in the highest good, in light and love.
After the dedication, you can either then program the crystal or leave it in the light of the sun or moon to energise.

Programming Your Crystal
You have obtained your crystal for a purpose, it may be for healing, protection, love, prosperity, peace. If you intend healing someone else, permission should be sought before programming begins. It might also be for the improvement of home or work environment,  or even seeking Angelic contact.
It is very important that programming is well thought out and properly focused. Imprecise wording confuses the crystal energy's but meticulous wording directs energy precisely.
First you must select the crystal that resonates with the intention you have for it. (The 'Crystal Directory', or 'Crystals Can Be Used For' and 'Colour Meanings' pages can be a big help to you)

When you have precisely formulated your intention, hold the crystal in your hands. Sit quietly with it, letting yourself attune to its energy. Let yourself be open to your higher guidance that is with you. When you feel in total harmony with the stone, state your intention firmly and clearly. You may repeat this several times to anchor the intention into the crystal. When you intuitively feel that the programming is complete, put the crystal down. Detach your energies from the crystal by taking your attention from it.
When the crystal has been programmed, you might like to make a special time each day to sit with it, asking that the energies be transferred to you. Depending on its purpose, you can wear the crystal, place it in your pocket or put it under your pillow at night.

Programming a Crystal for Someone Else
It is far better for someone to program his or her own crystal. If this is not possible, simply ask that the crystal will work for the persons highest good. Try not to impose your own ideas into the crystal.