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