Summarize:

Reach your thumb and forefinger into the tin or pouch, or break off a piece of your plug. If you are a beginner to dipping, your pinch really should just be a small amount between your thumb and forefinger, probably about the size of a quarter. As you get more used to the taste and strength, the size of your pinch can grow, depending on how long you want it to sit in your mouth and how strong of dose of nicotine you are looking for. Take your tobacco and put it down in your mouth between your gums and cheek of your lower lip. Pack tightly together so you don't lose any of the leaves, and accidentally swallow them. Snus packets can also be held in the upper lip. The effect is roughly the same, though you may create more juice in your lower lip. Chewing tobacco works because the nicotine seeps into your bloodstream through your gums, rather than by inhaling smoke. Dipping tobacco can just sit in your mouth as long as you can feel something coming from it. You can get up to several hours worth of nicotine from a pinch of chewing tobacco, much longer lasting than a cigarette. If the tobacco starts to get loose, and you are worried about swallowing, use your finger or tongue to tamp it down back into place. Having something in your mouth will produce saliva, which will mix with the tobacco. You don't want to swallow this juice, and it is meant to be spit out. If you are outside, you can just spit onto the ground, but if you are indoors, keep an empty water bottle to spit into.  When using a spit bottle, it is better to replace the cap when you set it down. You don't want to accidentally knock it over and spill tobacco spit. Because the tobacco from snus packets can't get loose, the juice you make is meant to be swallowed. The flavoring used in snus can make it less irritating than juice from other forms of tobacco. Do not swallow your tobacco. Once you are finished with the tobacco, either because you don't feel any nicotine or you are doing something that requires a clean mouth, take it out of your mouth. Grab the tobacco with your hand, pull it out, then throw it away. If you are near enough to a garbage can, you can also spit out your tobacco. There's no reason to keep the tobacco any more. Rinse your mouth. After you spit your dip out, you may want to rinse your mouth to get rid of any excess tobacco. Don’t use your spit bottle for rinsing, and be careful not to swallow the water you rinse with.
Take a pinch of tobacco. Place between your gum and cheek. Let the tobacco sit in your mouth. Spit as necessary. Throw out the tobacco.