Contrary to what you may think, marinade actually does not penetrate particularly far into meat—even over the course of a few days, the bulk of the aromatic compounds in a marinade will travel mere millimeters into the meat (the exception being salt, small sugar molecules, and some acids). In reality, a marinade is mostly a surface treatment, and not much benefit lies in marinating for more than half a day or so. If you'd like the flavor of the marinade to completely coat your meat, your best bet is to reserve some marinade and simply toss your meat with it after it has been cooked and sliced.

Here are a few ingredients you should consider when constructing a marinade:

Salt is absolutely essential. It is one of the few ingredients that penetrates and seasons meat deeper than the outer surface. I like to add my salt in the form of soy sauce or fish sauce, which are also very high in glutamates, adding extra savoriness to my meat.

Sugar when used in moderation will help the meat brown better on the grill, creating strong smoky, charred flavors. A touch of sugar also balances salt nicely.

Aromatics are mainly a surface treatment, but they can still be quite powerful. Garlic, shallots, dried spices, herbs, or chilis are all good things to experiment with.

Oil is often a primary ingredient in marinades. Many aromatic compounds, such as those found in garlic, are soluble in oil but not in water. The oil will help spread these flavors evenly across the surface of the meat, as well as lubricating and protecting the meat when it first hits the grill.

Acid can balance flavors, but should be used sparingly. It can denature proteins in the meat, causing it to turn mushy over time. With very acidic marinades, it's particularly important to not overmarinade—certainly no more than half a day.

Originally Posted by Saria

It was back in the '80s that gastronome Nicholas Kurti, a professor of physics at Oxford University, picked up a slice of lamb and a bottle of white wine and decided to test a commonly held belief. Can a marinade really penetrate and tenderize meat? After coloring the white wine blue so he could watch its progress, he poured it around a slice of lamb. After 36 hours, it had penetrated only 10 millimeters (.39 inch).

News of Kurti's discovery has been even slower to penetrate. Most of us still believe in the tenderizing effects of marinades (most commonly, combinations of acids, oils and flavorings). But this foodie and atomic scientist proved that although acids--vinegar, lemon juice and wine, for example--as well as certain fruit enzymes in papaya, pineapple, kiwi and fig sap do tenderize meat, the process is just too slow for normal use and the resulting change in texture is unpleasant. (When Kurti tried to speed things up by using a hypodermic needle filled with pineapple juice to inject a roast, the meat acquired a mushy texture.)

McGee advises against soaking meat for longer than two hours in an acid marinade. "Any longer than that and the meat will have a kind of mealy stuff on the surface. The structured meat tissue becomes tiny protein particles, fine for a pate but not what you want in a steak."

Originally Posted by Josephine

Truth of the matter is that you should salt your meat about 40 minutes before it hits the grill. When the salt first hits a steak, it sits on the surface. Through the process of osmosis, it'll slowly draw liquid out of the mat, which you'll see pool up in little droplets. As those droplets grow, the salt will dissolve in the meat juice, forming a concentrated brine. At this stage in the game—about 25 to 30 minutes in—your steak is in the absolute worst shape possible for grilling. That moisture will evaporate right off, leaving you with a tough, stringy crust.

Give it a bit more time, and eventually that brine will begin to break down some of the muscle tissue in the meat, allowing the juices to be re-absorbed, and taking the salt right along with it.
What does this lead to? Meat that is both better seasoned and more tender and moist when you cook it.

EDIT: Do use kosher salt, not regular table salt. The larger grains of kosher salt (which should more accurately be called "koshering salt," as salt itself is always kosher—kosher salt is coarse salt used in the koshering process) are easier to sprinkle evenly with your fingers, and will also draw more initial moisture out of the meat to dissolve than table salt.

I love to marinate with tequila (the better quality the better the taste!), garlic, lime, crushed pineapple and teriyaki sauce overnight.

Originally Posted by Saria

Originally Posted by scrills