Identify your use case: cocktails/drinks vs. baking vs. sauces/glazes (alcohol evaporates differently than herbal top notes).
Start with the listed ratio for your substitute, then taste as you go—Chartreuse is herbal and sweet, not just “minty.”
If your substitute is too intense (e.g., absinthe or extract), reduce the amount and add a small sweetness bump to smooth it out.
When using in baking or long-cooked sauces, add the substitute earlier for body or later for brighter aroma depending on the dish.
For extract/oil swaps, avoid over-concentration: add gradually and dilute with vodka or another neutral alcohol.