"I did not use all of the exact ingredients called for in the recipe" OR "I substituted for one or more of the ingredients: If you do not follow the recipe exactly, and you use different-than-called-for ingredients, then I can't guarantee that the recipes will work for you. I can't tell you how many times I have spent a lot of time troubleshooting problems with someone only to find out that they used pancake mix instead of a flour mix or they didn't use eggs in a recipe that calls for eggs, or they used an alternative sweetener in the recipes, etc.

"I have no idea if my oven is heating to the correct temperature because I don't have an oven thermometer in there": The answer for this is get yourself an oven thermometer (they are pretty cheap and I got mine at the local drugstore) and determine how your oven is heating. See my oven thermometer post to learn more. This will affect almost any aspect of your baking.

"I did not use the baking pan called for." Or, "I used a plastic or other non-standard baking pan": Using the proper-sized baking pan is very important. If you use a Bundt pan when a loaf pan is called for, or an 8″x8″ pan when a 9″x9″ pan is called for, then you will probably get different results than you would using the correct pan. Also, if you use a baking pan that is made out of a non-standard material (like plastic), you will get different results. Most often this is a gummy or uncooked center.

"I didn't check to see if my yeast or baking powder's 'use-by' date has expired": If you use expired yeast or baking powder, you are using a product that may no longer be good to bake with. Yeast is a living organism. If you use an expired yeast, there is a good chance that all of the yeasties have died, meaning that they will not eat the flour and then expel gas to help your bread or cake rise. This will cause your item not to rise and it will be flat.

"I didn't beat the butter and sugar or the eggs and sugar at all/very well": Not adequately beating the ingredients as called for in the recipe can affect the rise of your baking. The leavening agents (baking powder, baking soda, yeast, steam) only work on pre-made air pockets, they don't create air-pockets on their own. And I have found that gluten-free baking benefits so much from beating the fat and sugar or fat and eggs very well before adding the other ingredients. This will create a flatter than expected result.

Updated: 1/30/12