I just did a ginger beer where I used raw sugar that still had sugar cane molasses in it. If you use this kind, you will need to boil it to break down the sugar. It becomes as hard as a rock when it dries out. I've used the bottled molasses before, but it tends to be more expensive. If you're using ginger, you can buy both raw ginger root and ginger powder. A small bit of either goes a very, very long way and can easily overpower your beer. I would highly recommend brewing your beer, then adding the powder at bottling (or kegging time). Mix it in, then taste a sample. Start extremely small, then work your way up.
Using raw ginger, it's best to add it right before you boil your wort. It breaks down the cells and extracts a lot more flavor. Cut the ginger root and measure it before hand. For example, if you want to use half an ounce, cut a 1 ounce piece (so you have room for your fingers) and just grate half of it. Grate it over the pot, because if you use a bowl, it sticks to the bowl and it's just annoying. You'll also get more ginger juice. It makes it easier than trying to measure how much ginger you have after it has been grated. The ginger will also stick to your grater, so just wash it off with the wort in your pot (stick it in and shake it a bit). Probably too much info, but just some helpful stuff I noticed while brewing with it.