There are two main reasons people sometimes have trouble making a stir fry at home:

1. Adding a lot of things to your wok all at once will cool off your wok, which means the food will simmer or steam instead of frying. This is especially a problem with meat. And,
    
2. Not all the ingredients cook at the same rate, so if you add everything all at once, some items will either be overcooked or undercooked.

So, what can you do about it?

Here are some tips:

Your Wok Should Be Smoking Hot

To make a good stir fry, you really absolutely must have an extremely hot wok. (You can use a sauté pan, too.)

Not getting the pan hot enough is one of the most common problems for home cooks. This is true in general, not just with stir-frys.

Restaurants have extremely powerful stoves pumping out mega-high heat, which enables them to get a beautiful sear on meats and cook foods quickly so that they don't spend too much time in the pan.

If you've ever seen the gigantic burners they have in Chinese restaurants specifically for the stir-fry wok, they're called "volcanos" because they get so ridiculously hot. These things blast out 75,000 BTUs, which is about TEN TIMES HOTTER than the average burner on a home range.

Your high-end range might feature one extra-hot burner that approaches 12,000 BTU, and obviously that's the one you should use. But even with that, you simply don't have the equipment to duplicate what a cook in a Chinese restaurant is able to do using one of their volcano burners.

That's not to say you shouldn't try, but I want to illustrate what the challenges are going to be.

So since you can't produce the same heat, you have to heat your wok for a long time. I like to heat my wok for 5 to 10 minutes over the highest heat I can get. Just heat it dry with nothing at all in it.

I'll close the kitchen door and turn on the vent fan while this is happening. (Note: You can't do this with a wok with nonstick coating. The best woks are made of carbon steel.)

Once the wok is good and hot, I'll add some oil. And for stir-frying, I like to use the most refined high-heat vegetable oil I can get.

That's usually a refined safflower oil, and my second choice would be refined sunflower oil. These oils have the advantage also of being very neutral-flavored, so you'll taste the food and the seasonings, not the oil. Peanut oil is also a good choice, and it imparts a slight nutty flavor.

Don't Cook Ice-Cold Meat

Adding cold meat will instantly cool off your wok. To avoid this, let the meat sit out at room temperature for 20 minutes before you cook it. You can marinate it during this time with soy sauce and a little bit of wine. Then when you're ready to cook, remove the meat from the marinade, then drain it and pat it dry before you add it to the wok.

And speaking of meat, you'll sometimes see strips of beef already cut up for sale as "stir-fry meat." Your better bet is to just slice up your own sirloin or skirt steak or flank steak. It's an extra step, but you'll know what you're getting and it will be fresher. Remember to slice it against the grain.

Cook the Meat in Batches

If you have more than 8 ounces of meat, cook it in batches. Overloading your wok with meat will cool it off, and as the meat releases its juices, it will end up simmering rather than frying. Which means it will turn gray and tough rather than brown and tender.

First heat up the oil then add flavoring ingredients (like garlic and ginger), and then add the meat. Spread it out so it's not all piled up in the center. And don't immediately start stirring it around, either. Don't touch it for half a minute or so to give it a chance to brown. Then go ahead and stir it around until it's nicely browned.

Cook the meat until it's nearly done, then remove it and set it aside. Reheat the pan and add more oil if necessary, then repeat until all your meat is cooked almost all the way.

We cook it almost all the way because we'll add it back to the stir fry right at the end, and it will finish cooking then. Otherwise it'll be overcooked.

Cook the Vegetables Next

Once you've set aside the meat, heat up the wok again, add fresh oil and seasonings and then cook the vegetables. Things like onions and sliced mushrooms can go in early. Leafy vegetables like spinach or shredded cabbage go in at the end, and so would anything like bean sprouts if you want them to retain their crisp texture.

Some items like green beans, carrots and broccoli need extra cooking time, and I'll sometimes blanch them in boiling water for 60 seconds, then shock them in ice water and drain them completely. Again, it's an extra step, but the goal with a wok is to cook quickly so that you don't end up with a lot of liquid at the bottom.

You might add some soy sauce, wine or stock at this point, and cook until all the veggies are cooked. You want them to be crisp and retain their bright colors. Overcooked veggies will be soft and drab in color.

Add the Cooked Meat at the End

You just want to heat it back up again to finish the cooking. You can mix up a slurry of cornstarch and cold water and stir it in at this point to thicken the sauce. Combine a tablespoon of cornstarch and an ounce of cold water to form a paste, then stir it into the stir fry and cook until it thickens.

Finally, I like to add a few dashes of sesame oil at the very end, but not before, because pure sesame oil burns really quickly, so it's more of a flavoring than a cooking oil.