Active Meditation is the advanced form of meditation, because it combines remaining mentally active with meditating.
The first step is to relax and get comfortable. Some ways to get into the "meditative mood" are clenching all the muscles in your body and then relaxing them slowly, one by one. Other ways are lighting incense or candles.
Close your eyes and picture a scenario in your mind, like watching a movie--we've probably all done this in our fantasies. Choose scenarios like riding the waves of an ocean, walking through a forest and seeing animals and hearing nature noises, etc.
When you've done this long enough, you will slip into a relaxing dream-like state, sometimes called "alpha." This means you will be awake and aware of things, but you won't be easily distracted and your mind will be focused.
Now you can continue your own meditation--perhaps working on something within yourself or trying to change a way of thinking. This particular meditation works the best before doing an intense ritual or ceremony, such as Samhain or Invoking the Goddess, etc. It gets you in "the mood" to raise power, direct it, and release it.

Passive Meditation can be done anytime for any reason. I specifically use this meditation following an intense ritual or ceremony. Since I began the ceremony with the Active Meditation to help raise power, I use the Passive Meditation to bring myself back to a relaxed and peaceful state afterwards.
Find a place where you aren't going to be disturbed and sit comfortably. Some people prefer to lay down. Go ahead if that is more comfortable for you, but be careful not to fall asleep!! Putting on soothing music, (in the background) can help you relax. I like using buddhist chants, nature noises, and spiritual drumming CDs. Turn off the lights and burn some candles.
Now, close your eyes and picture an image in your mind. This image is "static", meaning motionless, the opposite of the Active Meditation. Some examples are: a cloud, the full moon, plants, a round ball of energy that does not move, etc. Choose something pleasant because you need to hold onto that image in your mind for a long period of time.
After you picture the image long enough, you will slip into "alpha." What you do after this point, is up to you: specific rituals, directing energy, healing rituals, or simply enriching your mindfulness.

The first step is to recognize the purpose. In fact, one of the first steps in doing witchcraft rituals is stating your intent to the Goddess. Do this now. Say it outloud so you yourself understand it.
Think about your favorite place to go. It might be the beach, a place from your childhood, a mountaintop; or even where you'd like to go someday. I sometimes choose the snowy mountaintops of Tibet.
Once you are comfortable, take a deep breath. Take yourself to that place and imagine everything you would see, hear, taste, feel, smell, etc. Concentrate on the scene to silence some of the clutter in your mind. For me, I would picture myself in Lhasa, hearing the church bells, smelling the incense, seeing the statues of Buddha.
Continue doing this and incorporate anything into your meditation ritual that helps you. It's your meditation exercise, you can write it any way you want!
Just remember that the mind is never really silent. We are always bombarded with thoughts, chatter, and clutter. The point of meditation or mindfulness is to simply focus your mind in the present, in the activity you are currently doing until you reach another level of consciousness.

Sit comfortably. On the palm of your hand hold a burning candle. Look steadily at the flame of the candle. Feel the light of the candle like air and imagine, while breathing in, how the light is inhaled. The flame has become like air, something you need for survival. Picture a stream of bright light flows into your chest. Now go on with the purpose for the meditation.

Each plant, animal, rock, and other entity has a spirit. This can be found in many religions: Wicca, Paganism, Witchcraft, Buddhism, Native American, Shamanism, and many others. These Nature spirits are psychically powerful, and are much less abstract and controllable than the Elementals that many who perform all of their rituals indoors are familiar with. Nature Spirits can be extremely powerful allies. It is possible to sense nature spirits, to determine if they are receptive to a ritual planned, and to have them actively participate in magickal workings if they are.
For example, birds may join the rituals, flying around the circle when energy was being raised, specifically invocations dealing with Air. Nature spirits often channel great amounts of power into the magick being performed. Let Nature channel her power into the magick in her own way. Do not approach them with disrespect, or by attempting to command them rather than listening to them. The Nature Spirits may flee or attack. Besides, the goal is to honor and harmonize nature with your magickal workings.
Working with Nature Spirits can also bring a deep sense of partnership with Nature, and bring new levels of attunement. As always, respect Nature, Mother Earth, and all her creatures. It is sometimes a good idea to find your own personal Nature Spirit, or animal guide, but it is not necessary.