Short answer: there isn't one. Considering the fuss made over meringue, I'd understand if you thought it was tricky. But aside from whisking your arm off (just use an electric mixer!), nothing could be easier.
Meringue is a fabulous Exhibit A of the magic of chemistry: put egg white together with sugar and you turn a chick’s gluey protein glop into delicious chewy, crunchy, or frothy sweet treat (meringues can be any one of the three).
There is a lot of mystique about meringue that, in my experience, isn’t warranted. There is a lot of belief in the power of copper, or of an acid such as lemon juice or cream of tartar, to make meringues rise higher and bond together to be more “stable” — but I spent most of my adult life making meringues with nothing more than a plain electric balloon beater and a ceramic or metal bowl, and no one has ever been disappointed with the results. Apparently the real risk that the acid and/or copper is meant to avoid is a certain “graininess” from over-beating — but I find it hard to believe that most people really face this problem, since beating is fairly tedious even with electric power, and if you’re like me, you’re glad enough to arrive at “done” and gratefully stop. That said, if you want the insurance policy promised by that hint of acid, I advise wiping the bowl you use with the cut edge of a lemon wedge and never minding about the cream of tartar. Or you could use a copper bowl, which releases ions into the egg whites to improve the bond of the bubbles, so to speak, making them less liable to collapse. Copper bowls being rather expensive, you could try achieving a similar effect with a copper whisk. I must confess that my own copper whisk, pretty though it is, doesn’t see much action! One thing to note: if copper is especially beneficial to egg-whipping, aluminum (or aluminium, as we English call it) is said to be detrimental. Stainless steel is fine.
What about plastic? Typically we are told never to use a plastic bowl for meringues, since plastic can hold on to fat particles more readily than steel, glass, or stoneware bowls. But there are many types of plastic, some of which are more glass-like than others. If plastic is all you have access to, I’d wash it carefully, dry it thoroughly, and use it anyway. But if you are an enthusiastic baker — even if not a frequent one — I’d hope that you would treat yourself to a mixing bowl of a different material. There is nothing wrong with plastic bowls — I use them all the time — but they are not absolutely ideal for every aspect of pastry-making. On the other hand, sometimes we stress the ideal too much and fail to realize that good results can come from most any equipment. What matters more is method, and the quality of your ingredients.
It’s amazing how much meringue can be made from a single egg white (or albumen). Because of that, I determined that to make meringue, one only needs about 2 oz or 57 grams of sugar per egg white. That works out to 4 tablespoons of sugar per albumen. Once you know that ratio, you can scale up your meringue as much as needed. You can also make as little as you need, which is usually a benefit to the home cook with only so many eggs available and only so much room in the freezer or fridge, not to mention people to eat the dessert.
Another piece of advice you will often see is that the egg whites should be “room temperature.” I have beaten egg whites not long out of the fridge, and again, I’ve never been disappointed by my meringues. I should think that the very act of beating them warms them up (because of friction). And it is said — though I haven’t specifically tested this myself — that eggs are easier to separate into yolk and white when they are cold. What I will say is that I’ve used eggs at various degrees of coolness, and their specific temperature is really not important, one way or another.