Its OK to do it by yourself - in fact this is how many, perhaps most, people get started. But its really quite nice to share the experience with others. Its considered very bad form to fall asleep. Flexibility is a definite plus, but not a prerequisite. There are many ways to do it, but there is no right way and no wrong way.
Some people think that their way is the only way.
These people should be avoided. Traditionally there was both a Gradual Path and a Sudden Path. But these days everyone just wants to take the Sudden Path. Having a quiet, natural setting is nice. Some people like to dress up in exotic costumes and even perform esoteric rituals when they do it.