Identify your recipe type (bread/loaf, muffins/cookies, pancakes, or thick batter).
Choose the closest swap: bran-mix for closest whole-wheat structure, spelt for similar wheat behavior, oat/flax for tenderness/fiber, or 1:1 gluten-free for no-gluten needs.
Use the stated ratio (1:1). Measure by weight if your recipe is sensitive to flour weight (especially cookies and quick breads).
If your substitute is finer/drier than whole wheat (like oat flour), add a small splash of liquid or let batter rest 5 minutes to hydrate before baking.
Taste and adjust next time: for less dryness, reduce bran content or increase liquid; for more wheaty depth, add a small pinch of extra whole-grain flour in the next batch.