(somewhat referenced from: "Living Wicca", by Scott Cunningham)
Prayer is the process of attuning and communicating with the Goddess and God. During prayer, we may call Them from the Moon, the Sun and the stars, from the seas, the deserts and caves, from the haunts of wild animals; from the Earth it's self: but the call must first move us, must first renew our awareness of the Goddess and God within, before it can contact the universally manifested deities. In prayer, we must narrow our focus, at first, upon the Goddess and God within, before we can contact the greater understanding of the Goddess and God. This initial focus may be accomplished through words, visualizations, songs or by other means. There are no governing rules, though a few suggestions are presented below. Experiment to discover the most effective technique. To begin, develop a prayerful attitude which consists of peace and hope resting on an unshakable spiritual foundation. One may then begin each prayer with the following words, [and I'd recommend to visualize Their presence, light, life and energy within you, as you say]:
O Goddess Within,
O God Within,
While saying these words, shift your consciousness to the warm, peaceful memories of previous contacts with Them. This may place you into the proper mode of consciousness. You could then proceed to say [you can and should certainly edit this to include that which you personally connect with the Goddess and God, though, all things are connected to Them]:
O Goddess of the Moon, the Waters, the Earth, Nature, love, psychic sight, and wisdom; O Horned God of the Sun, the greenwoods, the Forests, the wild places, the Harvest, and of death and Rebirth;
This expands your conception of the Goddess and God, and contacts a greater part of Them. Once you've achieved a stronger connection, you then speak to Them in specifics (i.e., state the reason for your prayer).
Wiccan prayer, then, isn't addressed to some distant deities who reside in alien cloud palaces. We needn't use a bullhorn to call to the Goddess and God. Rather, we need only become newly aware of Them within us. This is the secret.
The Goddess and God will always help and be there for you with love, comfort, assistance and answers (as long as one invokes these positive aspects of Them). Also, remember that much knowledge, luck and power is already within you, as is the "divine spark" of the deities and/or of the/Their Light. Appeal to the Universe with attunement, energy, respect and love, and your prayer will be answered. However, do not constantly dwell on the spell, prayer, rite, or ritual -- do it, then forget about it, and allow it to brew and cook and its work and the answer will come to you. You do not need to cast a circle, or do a ritual to pray; rather, one can and should pray at any time, though, prayer it's self can be considered a form of magic.
Spells generally last not longer than 30 days. Spells performed during the New Moon may take until the Full Moon to come to completion. Spells done at the Full Moon may need one full cycle of the Moon to show the most results. There are other time limits on them, such as one that would last from season to season, or from holiday to holiday, and there are some, such as vows or dedications, that may last one's whole lifetime (or beyond as Wiccan embraces reincarnation as one of it's concepts, though, it's not practical to set a vow for your next life; your soul may decide to do something else before then. Yet, I believe that it is felt within Wicca that if you are studying magic and/or the Old Religion, this is not the first lifetime that you have, i.e., you are continuing your learning). It's up to you to generally set or visualize whatever time limit, or lack there of, desired, otherwise, the "default" time of a spell lasting is usually around 30 days.
Remember the universal Wiccan law: "An ye harm none, do what ye will," and the karmic system that what you send out comes back to you.
Prayers, spells and rituals can be ended with: "I call you now, attend to me; this is my will, so mote it be!", or "By the free will of all, and with harm to none, as I will it -- so shall it be done!", or simply: "Blessed Be!", "So mote it be!", or "So shall it be," are fine also, or a combination.