Although Quakers used to wear distinctive clothing, most do not now. Quakers value simplicity and integrity. We dress to show respect to those we meet, not to glamorize ourselves, and each person expresses that in his/her own way. Many women wear simple makeup and jewelry, for instance. You will not feel out of place in "business casual," however. Remember that the Merion Friends meetinghouse is over 300 years old and most of its original architecture has been preserved. It is not air conditioned. There is heat, but not insulation, so it can be drafty near the floor in winter. Dress appropriately to the seasons.
Quakers originally used the familiar pronoun "thee" to show that they felt there should be no distinctions between how one addressed people of different social classes. The rest of the English speaking world came to be of the same opinion and stopped using different second person pronouns for formal and familiar usage. However, "you" became the default word, rather than "thee." Most Quakers today also use "you," though you may hear it used as a term of affection among close friends and family members.
Expect to be welcomed. We love visitors. But we do expect to have plenty of visitors who will not choose to worship exclusively as Quakers. We are available to answer any questions you have, but do not aggressively proselytize. Feel free to come as often or as rarely as you wish, or to continue to worship at another church as well.
Quakers believe that God communicates directly with each person, without the need for clergy or ritual to mediate it. The Meeting for Worship is basically a shared time for people to clear their minds of the clutter of their daily lives in order to be open to that communication. At times, people may feel strongly moved to share a leading they have received. These "vocal ministries" are to be spontaneous (people don't arrive at meeting planning to say anything -- nor planning not to say anything) and they are voiced only when people feel both that they have received this leading from God and that they are led to voice it during the meeting itself. There is also a period of announcements and open discussion after the meeting when other leadings can be shared.
Since Quakers do not have a "hireling ministry," the members of each meeting must share not only the spiritual duties usually performed by a minister, but also the practical ones. A "monthly meeting" like Merion Friends Meeting has a meeting once a month to handle these business matters. Business might be as mundane as arranging to have a roof replaced or as serious as deciding what actions we should take to respond to world events like a war or famine. Friends have a process for making decisions called "coming to unity." The meeting gathers just as it does in Meeting for Worship and members try to open themselves to God's leading in making decisions. All members must agree for a decision to be finalized; there are no votes nor majority rule. If anyone disagrees on a decision, they may choose to stand aside and let the meeting proceed while registering their disagreement, or they can continue to stand opposed based on their feeling of how God is leading them. In that case the decision is tabled for another time, as the one person opposed may be the one who has the clearest leading. (We often find the most serious decisions are the easiest to come to unity on and the simple ones drag on; God seems not to care what color the rugs are.) All are welcome to attend and contribute to the meeting for business (although in the case of a controversy the final decision would be made by unity of the members of the meeting). Quakers are also organized into quarterly meetings and yearly meetings, although the monthly meetings are where decisions must ultimately be accepted.
Quakers do not practice baptism by water. "There is that of God in everyone" already. Adults become Quakers by joining a particular meeting. Children are considered "birthright Quakers" until they become adults and make their own decision.
Yes, the Society of Friends went through several splits over the years, although most of the meetings in the Philadelphia area have reunited. Most of the meetings in this area have "unprogrammed" silent meetings for worship. Other Quakers, especially in the Midwest, have liturgical ceremonies and preaching as well as periods of silent worship. All Friends meetings have the same type of Meeting for Business, however. The Society of Friends began among Christians and the Bible is an important channel for God's communication. There is no historical controversy (even among non-Christians) over whether Jesus of Nazareth actually existed. The life of Jesus and his earliest disciples is the model for the radical Christianity the earliest Quakers sought to restore. However, Quakers may have different opinions on theological matters such as whether Jesus Christ is divine, whether particular biblical passages are authoritative, or what specific beliefs about Jesus one must hold in order to be considered "Christian." Texts other than the Bible are also valued, such as the writings of "weighty Friends" and other spiritual thinkers who have shared their leadings over the centuries. Quakers believe that "there is that of God in everyone," therefore God also communicates to non-Quakers and non-Christians. Many non-Christians are comfortable worshipping as Quakers since it is ultimately individual conscience that determines one's beliefs.