How do I make a marinade that actually works?

What a marinade actually does, the four components, and why overnight is often worse than an hour.

Difficulty: beginner
Time: 15 min
Read: 2 min
Safety: warning

Short answer

Fat, acid, salt and flavour. Salt does most of the useful work; acid tenderises the surface only and turns meat mushy if left too long. An hour or two is usually right, not overnight.

Marinades do less than people believe — they flavour the surface rather than penetrating deeply. Knowing that changes how you use them, and it explains why a long soak in lemon juice ruins fish rather than improving it.

Safety

Marinate in the fridge, never at room temperature. Never reuse a marinade that has touched raw meat unless you boil it first for several minutes. Discard it otherwise, and wash anything it touched.

What you'll need

Oil
Acid — citrus, vinegar or yoghurt
Salt
Aromatics
Non-reactive dish or bag

Step by step

Include the four components.Fat to carry flavour and stop sticking, acid for surface tenderising and brightness, salt for actual penetration, and aromatics for character.
Salt it properly — that is the part that works.Salt penetrates where the rest does not. A well-salted marinade seasons the meat itself; an unsalted one only coats it.
Keep the acid modest.Enough for flavour. Too much, or too long, and it denatures the surface into a mushy layer. This is the most common marinade mistake.
Match the time to the ingredient.Fish 15-30 minutes. Chicken pieces 1-4 hours. Beef and lamb 2-8 hours. Vegetables 30 minutes. Overnight is rarely better and is often worse.
Use a bag or a shallow dish.Something that keeps the marinade in contact with the whole surface, using as little as possible. Non-reactive — not aluminium or unlined copper with acid.
Marinate in the fridge.Always. Room temperature marinating is a food safety problem, not a shortcut.
Pat it dry before cooking.A wet surface steams instead of browning. Wipe off the excess — the flavour is already in the meat, not in the liquid clinging to it.
Never reuse it raw.It has been in contact with raw meat. Boil it hard for several minutes if you want to use it as a sauce, or throw it away.

Tips

Yoghurt-based marinades are gentler than citrus ones and tenderise without turning the surface mushy. They suit chicken and lamb particularly well.
A dry brine — just salt, left uncovered in the fridge — often does more for meat than a wet marinade, and gives better browning.
Sugar and honey in a marinade burn quickly. Fine for a quick grill, a problem for anything long on a barbecue.

Common mistakes

Marinating in acid overnight — Acid breaks down the surface proteins, and left too long the outside becomes soft and chalky rather than tender.
Cooking meat straight from the marinade, wet — The surface steams rather than browning, so you lose the crust and much of the flavour.

Questions people ask

How long should I marinate meat?

Fish 15-30 minutes, chicken 1-4 hours, red meat 2-8. Overnight is rarely better and acidic marinades left too long make the surface mushy.

Does marinade penetrate the meat?

Barely — only a few millimetres, and mostly the salt. The flavour is largely on the surface, which is why patting it dry and browning well matters so much.