Skills: Whisking
Whisking is an essential skill to learn, whether you're whisking egg whites, meringue or cream you need to know how to do it correctly and more importantly you need to know when to stop

The basic skill:
Hold the whisk loosely in your hand, if you hold it too tightly you will only hasten the onset of lactic acid.
Keep your whisking elbow pinned to your hip, rotate the whisk through your wrist, not your elbow.
Never use a small bowl to whisk, especially if whisking whites or cream, remember the bigger the better. Larger bowls give more length for the whisk stroke which will result in more air being incorporated into the ingredient of choice.
Hold the whisking bowl in the crook of your arm, whip the whisk from one side to the other and use the force of the whisk's impact to help shuttle it down along the curve of the bowl and back across to the opposite side.
Repeat this motion.
If your arm tires, change your grip from overhand to underhand. This posture uses different muscle groups which hopefully will not yet have fatigued.

Whisking Cream:
As you whisk cream it will incorporate air and begin to increase in volume.
As the volume increases the cream will reach several stages:

Ribbon: As you lift the whisk from the cream, it will fall back upon itself but should leave a trail or 'ribbon' across the surface. This ribbon will not immediately sink back in on itself but will hold firm.

Soft peak: When you lift the whisk out of the cream and invert it to a vertical position you will see that the cream forms a peak. Because the cream is still relatively 'soft' the peak will collapse or curve back on itself with the effects of gravity.

Firm or hard peak: Repeat the above motion, the cream will now have formed a peak that holds its shape, even if you gently shake the whisk.

Over whipped or 'split': If you continue past the stage of firm peak the fats inside the cream will begin to congregate into lumps. At this stage the liquid and fats inside the cream will no longer form an emulsion and will begin to 'split' apart. The cream takes on the appearance of cottage cheese and weeps liquid.

Science behind the dish: Cream
Whipped cream is a (semi) stable foam of liquid and air. As the cream is whisked air particles become trapped in the liquid, these air bubbles are stabilised by fat globules which form walls around the air bubble.
Over beating results in the fat globules breaking apart from the air bubbles and moulding together to form larger clusters of fat. As this happens the foam loses stability and breaks apart into separate layers of fat and liquid


Whisking Egg Whites:
As you whisk egg whites (or meringue; whites and sugar) the whites will go through all of the above stages.
The act of whisking whites results in proteins forming a supporting wall around air bubbles. It is this action that allows the whites to form a stable foam. However these same proteins can also cause the foam to 'split' (wherein parts of the liquid are forced out of this stable structure) to prevent this from happening and to aid a greater, more stable egg foam there are several tricks that can be used:

Add acid: Add a touch of lemon juice (1/2 teaspoon per 2 whites or add a pinch cream of tartar per 2 whites)

Use copper: Whisk the whites in a copper bowl

Avoid all fats: Fats act detrimentally to egg foams. Avoid all egg yolks or grease, thoroughly clean the whisking bowl before using

Using sugar: Sugar is added to make meringues and to give the foam greater stability, however if added too early it will slow the foaming process and decrease the final volume capacity of the whites. When adding sugar be sure to add it only after you have reached soft peak or stiff peak stages

Chef's Tip: Use fresh eggs to form a more stable foam. When separating the whites from the yolks make sure that there are no remnants of the yolk left behind. Pick any trace of yellow that you can find from the whites otherwise the white will not foam
Need to seperate 10+ eggs? Use only very fresh eggs; the yolks are less likely to split. Crack all the eggs into a large bowl, with your hands pluck the yolks from the whites; this is far quicker than manually seperating single eggs (in high quantities)

Science behind the dish: Egg Whites
The whisking process agitates the proteins found in the egg white. These proteins unravel to form barriers around the air bubbles that are trapped during the act of whisking. These same proteins also entangle the liquid found within the white, the result is a series of air bubbles and liquid molecules that are trapped between the unraveled proteins, ultimately forming a stable foam.