It has been my experience that when one meditates in a group of people with similar desires and beliefs, the meditation process becomes stronger and deeper. This is similar but stronger than the intensity one experiences in Holy places, churches, certain places in nature, etc. It is not necessary to follow a particular process. Each may meditate in his or her own way, simply absorbing the higher vibration generated by the group. People who engage in silent prayer within the structure of their spiritual services experience this same heightened awareness.
The jury is still out on guided meditation. If the guide is good, strong and pure of heart, it can be a wonderful experience . It is like one is riding the crest of a wave. If not, it can be either a neutral or negative experience. Music and/or chanting have also been useful in deepening the meditative experience.
Some learn to meditate simply for the physical and emotional benefits. Others are seeking a deeper meaning of life and their role in it. I believe that most groups seeking spiritual growth through meditation welcome all who wish to meditate with them, and require nothing in return. This is a way to benefit from group meditation as well as to learn about the particular spiritual path. There are Buddhist groups who host weekly meditation sessions in many localities and they do not require any change in one's beliefs in order to simply meditate with them. I believe the Society of Friends also welcome others to sit with them. A search on Google will produce more such groups if anyone is interested in exploring this area.