I call this "Weekend Stock" because it does take about 8 hours or so to make. Don't worry though, the actual prep time is closer to 30 minutes and is very easy, the other 7 hours and 30 minutes are letting the stock simmer on the stove. You should never leave a stove completely unattended so you can't put the stock on and leave for work however feel free to watch tv, clean, do homework, or play with your kids while it cooks.
1 Stock pot (I have an 8 quart one)
1 Mesh strainer
Large bowl for straining the stock into
Freezer safe storage bowls
Fill your stock pot between 1/2 and 2/3 full of water (depends on how much finished stock you want and the size of your pot). Throw in your stock ingredients (roast raw meat/bones first if you'd like a richer stock) and cook for about 7 hours or so. Check periodically to make sure the pot isn't boiling down too much, if it gets to be less than 1/2 the initial amount of water, add some more. When your stock is done, strain it into a large bowl through a fine mesh strainer to remove all the chunks.
If you made vegetable stock you can transfer the stock into smaller storage bowls now (or wait until it cools) and freeze any you aren't going to use within a few days. For meat based stock, allow it to cool in the fridge for a couple hours so the fat will solidify on the surface of the stock. If you have a very gelatinous stock (good for you! that's the best kind) you'll need to warm it up a little bit in a microwave or on the stove before you can transfer it to storage bowls. Freeze any stock you won't be using, refrigerated stock will only last about a week.
I haven't specified what to make your stock from. This is entirely up to you but for around a gallon of finished stock you should have at least a pound of stuff. What sort of stuff?
For vegetable stock I use about 1/2 a medium onion and a couple cloves of garlic, a few carrots and stalks of celery and then any other non-starchy veggies you have lying around (corn, green beans, peas, zucchini, tomatos, etc.) starchy vegetables like potatoes aren't very good for stock. This is a great way to use up fresh veggies that are past their prime and those leftover partial bags of frozen veggies that seem to lurk in the back of the freezer. If you like you can also throw in dried or fresh herbs if you have them. I avoid adding salt to stock, I can add it later if I need to but it's hard to remove too much salt.
For meat stock: Again use the onion and garlic along with any other aromatic veggies you have lying around like celery. Then add about a pound of animal bits, try for a good mix of meat and bones. I generally buy whole cut up chickens at the grocery store (only about 50 cents more than a whole chicken and I don't have to cut it up) which includes the neck and giblets. I save up these pieces in the freezer along with the bones from the chicken breasts after I've cut the meat off (either cooked or raw doesn't matter). When I have enough saved up I make chicken stock. The day after Thanksgiving is also good if you've made a turkey, just pick the good meat off the carcass for and throw everything else in the stock pot (same works with any other poultry, chicken, duck, goose, even cornish game hens though you would need several carcasses). For beef/pork/lamb stock you can buy soup bones at the store or use leftover bones from ribs and other bone in cuts of meat.