Here are instructions for using a homemade bin, open or closed. If you purchase your bin, such as a "Can-O-Worms" or a "Gusanito", follow the instructions that come with the system.
Things you'll need to start a worm bin:
A bin. See Build A Bin to decide which type of bin you'll use.
Bedding materials. See FAQ for information on different types of materials.
A nice, shady place to put your bin
Scraps for your worms
Once you decide on which type of bin you want to buy or build, you should set it up at least a few days in advance of receiving your worms. This isn't vital, but it makes the transition for your worms a little easier. This allows a little time for microbes to grow (which is what worms actually eat) on your bedding and food scraps. It's a much friendlier environment for hungry worms if you can let your bin sit for a few days before adding your worms. Don't have time for that? No worries, it's not the end of the world, it's just nicer for the worms.
Fill your bin about 2/3 full with the moistened bedding materials you have chosen. Save some dry bedding for the top of the bin to help keep out flies. I have successfully used shredded junk mail (no glossy or plastic), shredded paper grocery bags, shredded corrugated cardboard, coir (coconut husks) that has been rinsed of salts, and hay/straw. Most of my bins are some combination of a few of these materials. Your worms will eventually eat your bedding along with the food you provide them, turning it into castings as well.
When your bin is full of bedding, make sure that the moisture level of the bedding resembles that of a moistened sponge: not sopping, not dry. Now lay either a layer of food scraps, or put the food scraps over to one side of the bin, your choice. I like to spread my scraps out at least a bit because it helps prevent anaerobic conditions while the food decomposes, which can get stinky. You want to be able to get some air down there so that your compost both stays moist and doesn't compact too much and produce anaerobic sludge (VERY nasty, believe me!).
After your food scraps go in, put a nice thick layer of dry bedding on top of the whole thing. This bedding will keep out pests and keep things smelling nice. I really like using hay for the top layer; it's cheap and it smells really nice. But any dry bedding will do fine.
When your worms arrive, gently open the box or package. If this is your first time handling worms, you might freak out a little bit to see 1000 worms squirming around in front of you, but it's ok. Take a deep breath and say the mantra I use myself when I get overwhelmed, "They're just little animals. They're just little animals. They're just little animals." Pull back some of the dry bedding in your bin and gently turn out the worms into the bedding in one big pile. Don't spread them out; they're probably a little traumatized from traveling and they'll venture out into the bin when they're ready. Cover them up with the dry bedding. If there are worms left in the package, simply leave the package on the top of the bin for a day, pointing down so there's a clear path; the remaining worms will not like the light or dryness of the top of the bin and will burrow down relatively quickly. If you are using an open system, leave a bright light on for a few hours if possible to prevent any escapes from nervous worms.
Give your worms a few days to settle in before you bother them again. You may want to use a hand rake to dig into the bin on the edge just to make sure that the bedding down below is moist enough, but otherwise give them a little time before you feed them anymore. When it looks like they're starting to make it through the scraps, you can start to add more. Add your scraps every few days in little pockets around the bin, underneath the dry bedding. The worms will migrate to the fresh scraps as they finish the old ones.
Another way to work with your bin is to layer food and bedding like a lasagna. In this case it is not necessary to fill the bin as full of bedding when you first start, perhaps just 1/4 full of moist bedding instead of 3/4. Then, when you feed, layer food and then ample amounts of dry bedding (at least double the volume of what you are feeding). As the food breaks down the liquid will moisten each layer of dry bedding below it.