Anyway, all that said, I am not a baking master! Most of this information is stuff I've picked up from watching Good Eats, and the rest is from reading and experimenting. I'm definitely still learning, and I'll probably be referring to this page for a refresher from time to time, myself!
When I am not using a scale, I always use the spoon-and-level method for measuring flour. To do this, simply spoon flour from its container into your measuring cup and level with the spine of a knife. This is preferable because it will prevent you from packing too much flour into each cup and subsequently adding too much. Due to high amounts of gluten, excess flour will result in a heavy, dry and tough cake, which is hardly ideal!
To make a quick substitute for cake flour (which I can't be bothered to buy), take out 2 Tbsp of flour for each cup the recipe calls for and replace with an equal amount (2 Tbsp per cup) of corn starch. This isn't an exact substitute because cake flour contains fewer proteins and is milled more finely from of a softer part of the wheat than all-purpose flour, but trust me - it works just as well.
Large eggs are standard for baking, and they are the size I use in my recipes.
They should always be at room temperature to promote even baking and proper whipping. This can be achieved quickly by placing whole eggs in a bowl of warm to hot water after taking them out of the fridge. Give them 10-15 minutes and you're good to go!
But that's not all I have to say about eggs. Besides being delicious in their own right, eggs are very important in baking because they are emulsifiers. The phospholipids contained within the shell have the ability to latch onto both fat and water molecules, rendering your batter smooth and homogeneous. Without them, the fat (typically in the form of butter) would never completely mix with the liquids and you would end up with a nasty, curdled mess that won't bake up correctly. That said, properly incorporating eggs will ensure a nice rise (in conjunction with leaveners) for a fluffy crumb, and also add tenderness to your baked goods. Beat batters well after adding each egg, continuing until they are significantly fluffier before incorporating the next.
When separating eggs, it is best and easiest to do so immediately after taking them out of the fridge. This is because the cold causes the proteins in the white to become more tightly wound and the fats in the yolk to become more solid. Together, these two factors make it less likely that a yolk will be broken in the process of separating.
For meringues, it is important that you do not get ANY egg yolk (or other fat) into the bowl you plan to whip the egg whites in. If fat does get into your bowl, it will coat the proteins in the egg whites and prevent them from forming bubbles. To ensure that you never spoil a bowl of whites, separate each egg over a small bowl, and transfer each white to a second bowl. That way, if you mess up, just toss the white, wash the small bowl, and continue.
I use regular granulated sugar in most recipes as I can't be bothered to source or buy super fine sugar. If I am without a scale, I use the spoon-and-level method when working with confectioner's/powdered sugar to ensure that I am not packing too much into each measure. Brown sugar should be lightly packed, but be nice to it - don't completely compress it!
This may come as a surprise to you, but in addition to serving as a sweetener, sugar also keeps baked goods moist. Because it is hydroscopic (water loving), it attracts and absorbs water from its environment, slowing the effects of retrogradation (staling). It caramelizes under intense heat (which is why cakes brown in the oven) and tenderizes by interrupting gluten formation.
Ah, butter. Please don't hate on the butter - it's so important for baking! It helps with texture and tenderizing by coating flour proteins with fat to prevent them from forming gluten. In that same strain, it makes things moist, and... Well, it just plain tastes good!
I always use room temperature unsalted butter unless otherwise stated. Also, P.S., Margarine is not a suitable substitute because it contains more water than butter and will throw off your ratios!
This is a very important step in making a cake, as it is the first step in which air is incorporated into the batter. When beating together room temperature butter and sugar, the tiny sugar crystals cut into the fat, creating tons and tons of tiny bubbles. These bubbles will expand when heated, making cakes tall and fluffy when baked.
I know what you're thinking: what about leaveners? Yes, they are important, but they can only do so much! Beating an adequate amount of air into the butter gives your cake all that much more of a lift. The whole process should take about five to ten minutes and involve lots of bowl scraping! Properly creamed butter and sugar will be visibly lighter in color and fluffier after the time has elapsed.
I don't know about you, but folding scared me when I first started baking. An integral step in making chiffons and sponges, it requires a gentle hand and a watchful eye to pull it off, keeping as much air in the batter as possible. To begin, always add the lighter mixture to the heavier one. Add about 1/3 of the mixture to begin, using a rubber spatula to divide the batter in half by cutting straight through the center, then down along the bottom of the bowl, up the side and over the top to the center. Turn the bowl slightly and repeat, folding until just a small amount of streaks remain. Add another third of the batter and repeat, finally adding the last third and folding until no streaks remain. The resulting batter will be quite light!
There are a variety of ways to cut fat into flour. I learned to do it by using a fork to press frozen butter into pastry, but some people do it by rubbing the fat and flour gently between their fingertips. You can buy pastry blenders at most stores, but I find them to be quite unnecessary. Food processors, on the other hand, are a modern and quick way to get the job done. Just a few pulses will suffice!
Anyway, when working with butter for pastry, you must always keep it cold. Ice cold. If it melts or gets too soft, your pastry won't be flaky or light when baked. This is because the liquids in the butter won't be able to expand and evaporate in sheets as they are heated, which will make your crust flat, chewy and sad.