Ask yourself how many meals you'll need to prepare (choose the meal you struggle with the most). Be realistic with your time and skill level. Choose lean proteins, low carbohydrates, and add non-starchy vegetables.
Choose recipes with similar ingredients to make meal prepping more efficient.
Take inventory of what you already have. Categorize ingredients for an efficient shopping trip.
Wash and chop all veggies, marinate all meats, etc...
Prep can be anything from cooking an entire meal to prepping just the ingredients to be cooked.