One of the main challenges (of any type of frying) is making sure that the food cooks all the way through while the exterior browns and crisps simultaneously, all without becoming greasy. The most important factor is making sure you fry using oil that is in the correct temperature range (which we specify in our recipes).
Cooking in batches to avoid overcrowding helps ensure the oil temperature stays in the correct range. Letting the oil come back up to temperature between batches of food is also critical. (This won’t take long when shallow frying, since one of the technique’s advantages is that, with less oil to contend with, the oil heats for subsequent rounds more quickly.)