Step 1 : pick the right formula. If you know your body fat % (reliably measured), use Katch-McArdle. Otherwise, Mifflin-St Jeor.
Step 2 : validate your activity level. Don't confuse "active in the gym" with "active in daily life". A desk job + 4 sessions/week = "Light" for the multiplier (workouts only account for ~5-7 % of waking hours). If you are a manual worker or postman + training, then "Active".
Step 3 : set your goal. Cut : moderate deficit 15-20 % (loss 0.5-0.7 %BW/week max to preserve lean mass). Maintenance : at your exact TDEE. Bulk : surplus 5-10 % (gain 0.2-0.4 %BW/week to limit fat gain).
Step 4 : choose your macro profile. For 90 % of athletes : balanced or high-protein. Low-carb if you tolerate carbs poorly (digestion, roller-coaster energy). Ketogenic only out of personal preference or a medical contraindication to carbs.
Step 5 : track your weight for 2 weeks. Daily weigh-in on waking, weekly average. If loss/gain is outside the range, adjust by 100-150 kcal (no more, to avoid yo-yoing). Recalibrate every 4-6 weeks.
Step 6 : fine-tune your protein intake. Minimum 1.6 g/kg at maintenance. In a prolonged deficit, raise it to 2.0-2.4 g/kg to minimise muscle loss. In a surplus, 1.6-1.8 g/kg is enough (the calorie surplus does the work).
Special cases : women in the luteal phase should plan for +50-100 kcal on expenditure (BMR ↑ 3-5 % in the luteal phase). Athletes in a prolonged cut (>12 weeks) should include refeeds or diet breaks to normalise leptin.