The Fivefold Kiss is a ritual greeting, given for a variety of reasons. It is often given during specific rites and ceremonies such as handfastings, initiations, Sabbat celebrations, and other celebrations. It is typically done in a group setting, however Solitaries are not left without options. Simply choose a desirable oil and anoint the five points of the kisses on oneself, taking them to mean the kisses of the Deities (you, of course, may desire to choose specific Deities, but it isn't necessary) and a blessing for yourself. The Fivefold Kiss is a lovely acknowledgement of our own divinity, because it is symbolic of the respect the God and Goddess give to one another, in mutual acknowledgement of importance and love.
Typically the Fivefold Kiss is given to a woman by a man, and to a man by a woman. The reasoning behind this would be that the male-female polarity is considered an institution in the traditional circles for which it was invented. It is by no means a rule, but mayhaps a rule of thumb. More often than not, it would depend on the tradition of the Witches in question, as well as personal preferences and beliefs.
The Fivefold Kiss is performed within the circle, and is not intended to be a regular greeting. As stated above, it is a ritual greeting, and moreover a blessing. Each of the eight kisses is accompanied by a blessing. Yes, there are eight kisses to the Fivefold Kiss. The 'five' in 'fivefold' refers to the five points of the body you are blessing.
Due to the wording of the blessings expressed in the Fivefold Kiss, it is thought that the origin of the term "blessed be" may be with this ritual.