If you're going to a plein air event, the best plan is to ask the event coordinators if they have a supply list for what you should bring.
Some questions to ask:
Will you need to mat / frame your art, for an event-sponsored art show?
If yes, then bring *all* the framing/matting supplies that you'll need for the show, plus maybe a couple of spares. Make sure your paper fits your frames (HINT: bring a rectangle of cardboard the right size for the opening in your pre-cut mat. The idea is you can trace the cardboard in pencil onto your paper, and if you paint inside the rectangle, you end up with a painting that fits your mat / frame). You can do a lot of your framing prep work at home, such as installing the D-rings, gluing your business card on the back, etc. Make sure your frames are packed so they don't get damaged in transit. Old towels work great, layer towel / frame / towel / frame, and put them in a box or some container that keeps them from sliding all over the car.
What will the weather be like? Obviously bring the right clothes for the weather.
What is the dress code for the various events (will you need to clean up & get out of your paint clothes for a reception, or a dinner at a nice restaurant?)
If you're hiking in to a painting spot, what will the hikes be like, and are they transporting people's art gear, or will you need to haul your own food / water / art supplies?
What will the roads be like -- will your car need to be able to handle rutted dirt roads, or is that not an issue?
If it's a watercolor event, and you're in an area where it might rain, bring an alternative art supply, such as pencil, that doesn't get ruined by the slightest rain shower (I learned that on a watercolor trip to Ireland... I did lots of graphite pencil drawings on that trip, because every time I set up to do watercolor paintings, guess what. It started to rain!)
If you know any other artists who have been to this plein air event before, ask them for tips on what to bring -- and just as important -- what not to bother bringing.
Some plein air events offer more programming than anyone can possibly do, and still enjoy the event. The people who have the least fun are the people who feel they have to do absolutely every program on the agenda. Think of this as a buffet -- if you eat everything on the buffet, you'll feel sick from overeating. So... feel free to pick and choose the programming that appeals to you, and also feel free to ditch the events that don't. Except obviously if there is a more or less required part of the programming that you're expected to do, like registration, or a big artists' reception, don't ditch that.
Good luck, and congratulations! Above all, have fun.
