Use the recipe's size and amount
For a first attempt, avoid changing the egg size, flour, and dairy together. A batter's thickness or a cake's texture can be difficult to explain when several ingredients have changed. Write the size in your notes if it was different from the formula.
Crack into a small bowl first
A separate bowl makes a piece of shell easier to find and prevents a spoiled egg from entering the entire mixture. Add the egg once checked, then use the bowl again only when it remains suitable for that raw-egg stage. Keep raw egg away from ready-to-eat garnishes.
If separating eggs, have the containers labeled before starting. Keep the whites free of yolk when the recipe needs them for whipping. A small accidental yolk streak is easier to deal with in one egg's bowl than after it reaches all the whites.
Plan any uncooked use carefully
For preparations served with raw or undercooked egg, FDA recommends pasteurized shell eggs or pasteurized egg products. That includes certain dressings, sauces, and homemade frozen desserts. A familiar family method does not replace the safe ingredient choice.
For cooked egg dishes, use reliable temperature guidance and a recipe intended for the product. Keep eggs refrigerated as their package and local guidance require. Wash hands and equipment after raw-egg preparation, including the whisk you might otherwise reuse for a cold sauce.
Give extra yolks or whites a real plan
Before beginning a recipe that uses only one part, decide whether the other part has a near-term use. Keep it in an appropriate labeled container and follow official storage guidance. A row of unmarked cups in the refrigerator is an avoidable puzzle.
Choose a second recipe deliberately rather than adding extra egg to the first one because it is available. An extra white or yolk changes moisture and structure. If you want to experiment, record it as an adaptation and keep the original formula nearby for comparison.
Keep in mind
Do not taste raw batter. Flour can carry harmful bacteria as well as raw egg.
Egg substitutes differ in composition. Use a recipe or adjustment guidance developed for the particular substitute.

