Here's a collection of cake bakingtips and tricks I have collected over the years. Hope this helps.
1. I do use boxed cake mixes when in a bind, but I try to make the frosting from scratch. There are many doctored box cake recipes that taste as good as baking from scratch. Home made buttercream definitely masks any boxed cake mix taste.
2. Measuring flour: This I have learned the hard way. For baking, flour is best measured by weight. But I don't own a scale (shame on me) and most recipes just mention cups..so the second best method of measuring flour is to spoon it into the cup with a light sprinkling action and then level off with a knife. Dragging the cup through the flour ends up packing the cup with a lot extra flour resulting in a much drier denser cake/bread.
3. Room temperature ingredients: Its best to work with all ingredients at room temperature. Liquids like milk, water etc can always be nuked in the microwave until barely warm (not hot!). Make sure butter is soft but not greasy/melted..if so pop it into the fridge for 2 minutes. I have not learned any tricks to getting butter softened quickly (sorry!) Also eggs are best at room temperature but I never seem to remember to take them out an hour in advance. A trick I learned from the web is to submerge the eggs in a bowl of warm water for a few minutes until they do not feel cold to the touch. Works like a charm! I definitely see the egg liquids are much looser and whip up better this way.
4. S-M-L-XL: Eggs in the US are sold by size. I've learned that recipes usually mean "Large" eggs. Recipes should specifically call for M or XL eggs if required.
5. Greasing the pans: I spray my baking pans with Baking Joy (its a grease+flour spray that works very well for cakes). Alternatively, you could use Pam or butter and then dust it with flour. I also use parchment paper rounds at the bottom of my cake pans, it takes the stress out of getting the cake bottoms smooth and out of the pans without ripping. They're not perfect circles but I try to get as much of the bottom covered.
6. For dark pans, lower the oven temp by 25 deg F. Also he lower the temp, the less the cake will dome. I'm going to try and buy aluminium pans only going forward. The next time I go to India, I'm going to go shopping for pans...they're way cheaper there I think!!
5. Cutting cakes: Joe Pastry (http://www.joepastry.com/) does an entire post on how to cut a cake the right way...its worth a read, when you want clean cake slices.