You're going to get a different opinion from just about everybody that replies.
Chicken is one of the easier things to smoke, but there are still pitfalls.
Here's my tried and true method for some pretty consistently great chicken.
1. Keep the chickens under 4.5 lbs. The reason here is that a smaller chicken will be a younger, more tender chicken. Up over 5 lbs the birds will have more flavor, but can be quite a bit tougher.
2. Brine. A simple ratio of 1 cup kosher salt and 1 cup sugar to 1 gallon of water is all you really need. Other ingredients are optional. Heat to dissolve the sugar and salt then cool to room temp before adding the bird. Leave in the brine (in the refrigerator) for as little as 2 hours to overnight. 8 hours would be about the max. You're going to hear a lot of people saying they never brine and have perfect chicken every time. This may well be the case, but I've been cooking chickens a long time, and I've had my share of disasters. I've never, however, had a properly brined bird dry out.
3. Spatchcock. This is the removal of the backbone and keel bone, letting the bird lay flat. This will assure your white and dark meat cook evenly and are done at the same time. It also makes carving a whole lot easier and quicker.
4. DRY. This is the most important, and most often missed step. After brining (or after washing if you don't brine) set the bird out on a cooling rack in a sheet pan, uncovered, in the bottom rear of your fridge overnight. 24 hours would be better. Sprinkle the skin with salt beforehand. This will not only dry out the skin, but will coax proteins to the surface which will form a pellicle of sorts, aiding in browning and smoke absorption. It will also allow the skin to "crisp" and be tender. This step DOES NOT dry out the meat.
5. Smoke. At 325˚. I like your choice of hickory, as it will give a good hit of smoke in the short time the birds will be in the smoker. Cook time should be under 2 hours for a 4.5lb bird at 325˚. Brush the skin with olive oil or butter at the beginning. Season however you want. I like to use only salt, as it lets the beautiful brown skin show and also highlights the flavor of the smoke and the chicken. I also like to baste with butter at about the halfway point. Take the breasts to 165˚ at a minimum, or as high as 175˚ if you're serving guests. At 165˚ it'll be perfectly safe, but there can be some pink around the bone in the dark meat which freaks people out. At 175˚, if you've brined, it will still be perfectly moist and the dark meat will be more done.
6. Carve. A properly spatched bird is carved with 5 moves of your knife. One to cut the bird in half lengthwise. 2 and 3 to separate the breasts from the leg quarters, and 4 and 5 to separate the thighs from the drumsticks. I leave the wings on with the breasts.
7. Bow. You're going to get a round of applause from your guests when they taste this chicken.
