Similar to the Christian, Jewish, or Islamic counter part, a Pagan priest or priestess is a figure of importance in religious gatherings. They are responsible for the planning and overseeing of a ritual; they symbolize the Lord and Lady in a physical presence.
In the past, a person was chosen for the position of priest or priestess by body markings, like an extra finger or tow, or by a strange birthmark. Perhaps your mother and/or father were once a priestess or priest, chances are you will follow in their footsteps. On method I thought extremely strange, until I thought about it, was being struck by lighting. If you were struck, then you were (if you survived) made a priest/ess.
I say 'until I thought about it' because war are talking about a day and age where lighting was an unexplainable phenomenon. It was divine as its origins were unknown. Therefore, if you were touched by this divine energy and survived, the you were a great being.
Becoming a priest/ess means you are letting yourself become more open to the divine. In so doing you allow yourself to work with more difficult energies. The first responsibility of the priest and priestess is to symbolize the union of the Lord and Lady, or the Sacred Marriage. Though important always, it becomes especially important during the spring fertility festivals where this union is seen as creating all the new life.
Other, not so important responsibilities are being able to divine the future. The future was important to our ancestors, to predict whether the year would be dry or wet, whether the winter would be mild or harsh. Another great skill is that of working with the weather. Being a "weather witch" is one of the most difficult skills to learn. There are few who can do it and even fewer who can do it well.
Aside from magick, the priest and priestess "dress for success". That is, they dress for the season they are celebrating. Clothing can be a very powerful thing. In India, people sew mirrors onto their clothing to reflect negative energy. Wearing a certain shirt or dress makes you feel more powerful, happy, or energetic. Clothing worn during ritual should give you power, help you stay grounded, or such.
Below is a list of the seasons and the robes/colors to be warn by each. (PS stand for priestess, P stands for priest.)
Yule--> PS: red-symbolizing the Goddess in her mother phase; P: white-symbolizing the divine child
Imbolc--> PS: silver, gray, or white-symbolizing the Goddess in her maiden phase; P: indigo
Ostra--> PS: yellow-green-the buds of spring, pink-the sunrise; P: green-leaves
Beltane--> PS: white-the Goddess@marriage; P: green-the God@marriage
Midsummer--> PS: red-flame; P: gold-sun
Lammas--> PS: red-motherhood, gold-harvest; P: red-sacrificed, gold-harvest
Mabon--> PS: black-crone; P: purple-sacrificed wine god
Samhain--> PS/P: black-death/spirit
