Bitterness is a normal part of coffee, but it should not overwhelm sweetness and aroma. When a cup tastes drying, burnt or aggressively bitter, change one variable at a time.
First, check the beans
Very dark roasts often taste smoky or bitter regardless of technique. Beans also lose sweetness as they become stale. If every brewing method produces the same burnt character, try a fresher medium roast before rebuilding your recipe.
Grind slightly coarser
Water extracts coffee more quickly from smaller particles. If a pour-over or AeroPress tastes bitter and finishes slowly, make the grind a little coarser. For espresso, a coarser adjustment can shorten the shot, but weigh the result so you know what changed.
Reduce contact time
Longer brewing generally extracts more. Shorten an immersion brew by 15 to 30 seconds, or stop a moka pot before its final sputter. With pour-over, a coarser grind often reduces total time naturally.
Use slightly cooler water
Water just off the boil works well for many light roasts. Darker coffee may taste smoother with cooler water. Let the kettle rest briefly and compare the result. Temperature is usually a smaller adjustment than grind, so start there only after checking the obvious issues.
Clean the equipment
Coffee oils become stale and bitter. Rinse removable parts after use and periodically clean grinders, brewers, carafes and reusable filters according to their instructions. A spotless recipe brewed through an oily machine will still taste unpleasant.
Keep a short note
Write down the coffee dose, water amount, grind setting and brew time. Change one thing, taste again and keep the adjustment only if it helps. This avoids chasing the cup in circles and quickly builds a recipe that works for your equipment.