You can find a number of pre-made building plans online, showing you exactly how to make all sorts of different buildings yourself. This is great for beginners, who haven't gotten used to the materials available to them yet.  Minecraft Building Inc is one great example. There are a couple of sites on the net that will let you create your own building plans, drawing out exactly what materials should go where. The most common site for this is MineDraft. There are loads of videos on YouTube that show you how to build cool houses and other fun structures. Spend some time exploring and getting ideas for what other people have made.

Summary:
Use building plans. Use drafting tools. Watch YouTube videos.