I do chickens in the kettle but have used the WSM for them many times. I just sit the chicken on the grate. No water in the pan (foil it though).
You can
ice the breast(the linked post plus the few below), if you wish, which can be helpful to even cooking but it is not essential. I usually mix some softened butter with seasonings and work it under the skin, between the skin and the breast meat, right on the meat. (Gently loosen the skin first, with your fingers (extend your reach with a spoon, bowl down), starting from the neck end. Work the butter onto the breast meat, both sides, then turn the chicken, if necessary, and do the same thing from the large cavity side if you weren't able to quite reach it from the neck side.) I then lightly oil the ouside of the bird and season it all over. Inside the cavity I season as well and often toss in a quartered onion, say, with several crushed garlic cloves and maybe a lemon half or two.
If I am going to ice the breast, I do the skin/butter thing first, about two hours before cooktime then ice the breast. Just before cooktime I quickly oil the skin, season, chuck whatever into the cavity, and pop the bird into the cooker.
If I don'tice the breast, I prep the bird about an hour-90 min before cooktime so it doesn't go in cold.
If I use wood it is just one small piece.
That's my way. Pretty simple.