In the age of abundant access to books and the Internet, the ability to practice as a Solitary Witch has grown. It would be impossible to guess how many practicing Witches there are today.
Today's Witches practice in two ways: Solitary and Coven.
A coven is a group of Witches, usually no more than 13, that follow a specific tradition with its own rules and ways. There are usually different levels of initiates in a Coven and joining one requires a great deal of time and commitment. Because of this commitment, it is very important that you research the traditions of your perspective Coven and meet its members before you consider joining. This is an important decision and you need to make sure you chose the right one. Do not take this lightly.
It is an individual choice to join a coven or not. Some people like group settings; others prefer solo work. Being in a coven doesn't make you any more of a witch than practicing solitary.
There is also a third option. Some Witches prefer to work solo but like to occasionally gather with others on Sabbats. If you do some searching, you might be surprised at how many open circles there are nowadays. These allow you to experience ritual work in a group setting without the commitment of joining a Coven. Many magick and occult shops also hold open classes and workshops if you are craving a group setting or just want to meet others.
Any Witch can, and should be, dedicated. Dedication is when you pledge to follow the path of the Goddess and God, sort of like a Christian baptism. It is a very personal decision as to when and how to do it. This is also the time that (some) Witches traditionally chose their Witch name as part of their "rebirth" into Wicca.
Some covens also have dedications into them. A Witch is a dedicate to a coven for a specific time, usually a year and one day, before they become initiates.
Only Witches in covens are initiated Witches because, technically by definition, you need someone to initiate you in order to be initiated. However, there are exceptions to everything, for example, Family Traditions may have their own initiations without being a traditional coven.
Some coven Witches have an elitist attitude to them, believing that only those who have been initiated into a coven are "Wiccan." This is simply not true. Who initiated the first Wiccan? As Scott Cunningham so eloquently said: "Some say only a Wiccan can make a Wiccan. I say on the Goddess and God can make a Wiccan. Who is better qualified?"
"When the Old Ways have become a part of your life and your relationship with the Goddess and God is strong, when you have gathered your tools and performed the Rites and magick out of joy, you are truly of the spirit and can rightly call yourself 'Wiccan.'" (Scott Cunningham)
*From Bewitching Ways*