Guided meditations may sound sort of passive, but they are actually hard work. You must exercise all your visualization skills to follow the instructions of the leader of the meditation, and that is good for you.
The best guided meditations are multisensory experiences. That is, the best ones require you to use all your inner sense: seeing, hearing, feeling, and sensing (just knowing). To do that, you need to go into a trance, generally speaking, the deeper the better.
When you are being led by a (hopefully) skillful leader with a good voice in a planned, structured guided journey, you can easily achieve levels of concentration (trance) that you would not normally reach on your own. Once you have experienced that, it easier to experience it again. Eventually you can get there on your own.
Learning to experience multisensory trance has many benefits. One is that you can do trance work to make faster progress in transforming your consciousness. In other words, it is a boost to your spiritual development.
The skills you use in following a guided meditation are the same ones used in doing spiritual or psychic readings, doing healing, hypnotizing yourself, relaxing deeply, and even in shamanic journeying.
The best guided meditation would be one that is done in person by a highly skilled guided meditation leader, but those are not so easy to find. The next best thing may be a really good guided meditation CD.
There are many guided meditation CDs on the market. Try some out to see which ones work well for you.
One guided meditation CD that I can wholeheartedly recommend is Flow-Dreaming, by Summer McStravick. McStravick is a broadcast professional with a pleasant, unaffected voice and manner. Her special form of guided meditation takes you into the universal flow and teaches you to create real change in your life and your world in a joyful, fun way.
The Flow-Dreaming CD comes in a beautiful little book that explains what flow-dreaming is and how to do it. I have played the Flow-Dreaming CD for my journeying group, and they loved it, too. The Flow-Dreaming book-and-CD set is very inspiring and makes a wonderful gift—for yourself or for others.