A few things I would recommend:
1. Fresh blueberries - I found that if you start using frozen blueberries it messes with the cooking time. The inner part of the muffin takes longer to cook and the outer part of the muffin burns a bit.
2. Use small blueberries. If you use large ones they seem to sink to the bottom and clump. I like my blueberries to be more spread out instead of just making a mushy mess.
3. If you're baking these at lower altitude this recipe might work as it is or your might need to remove a few things such as 1/4 - 1/2 c. of four and maybe an egg.
4. The pumpkin puree can either be from a can, fresh roasted pumpkin, or even pumpkin you've roasted and then boiled into a beer. As long as it's pumpkin, cooked, and pureed it should be fine.
Step 1: Ingredients
1 tsp baking soda
1/4 tsp cinnamon
1/2 tsp allspice
1/2 tsp ginger
1/4 tsp ground cloves
1/2 tsp salt
2 c. sugar + another tbsp or two
1 c. pumpkin puree
1/2 c. canola oil
3 eggs for muffins (if you want to try to make small loaves I would throw in an extra egg)
1-4.4oz package blueberries
1 c. chopped cranberries
Step 2: Mixing the Ingredients
2. Mix wet ingredients in another bowl (except cranberries and blueberries)
3. Combine wet ingredients with dry ingredients. The batter will be just a little less viscous than cookie dough.
4. Stir in cranberries.
5. Gently stir in blueberries.
Step 3: Baking
7. Spray the muffin pans with pam. I've used the grease-and-flour method for a while and just realized that pam is easier
8. Fill the muffin tins 3/4 full with the batter.
9. Bake 30 minutes. Test the muffins with a toothpick to make sure they're done.
10. Remove the muffins from the oven.
11. Use a knife or spoon handle to make sure the muffins don't stick.
12. Let muffins cool on a cooling rack.
Notes: I would not recommend wrapping these in foil. The time I tried aluminum foil it ruined the nice crispy muffin top crust and made it moist. It wasn't quite as tasty without the crust.