Spend some time finding out what type of trees are native to the area in which you live, as this will help you determine what type of wood is available to you. Visit your local timber merchant and explain what you want to achieve, and he will help you pick out the best wood for the job.
Use the Adirondack link in the Resources section of this article to download a free plan for making a rustic chair. A chair is a good project for beginners, as it is relatively easy to make. The processes used to make a chair are the same as those used for making other types of furniture, so once you have perfected a chair, you can use your new-found skills to create other types of furniture. Taking these plans with you when visiting the timber merchant will be helpful in determining how much wood you will need.
Follow the plans. Ensure that you pre-drill all holes if you are using green wood, because if you drive a screw straight into this kind of wood, it will crack and split when it dries.
Use a slightly smaller drill bit than the screw when pre-drilling the holes. This way, the screw will really bite into the wood and hold it tight, especially as the wood dries.
Purchase or gather about 20 percent more wood than the plans state you will need. You could potentially make a mistake and need more wood than planned, or you might simply decide you don't like the appearance of a certain piece of wood. Either way, it is unlikely the extra wood will be wasted.