Professional Interior Designers always draft a scaled sketch of every room before beginning any work it. This is necessary first to make sure that the client approves the layout, but also to make sure that you purchase the right size pieces for each space. You don't have to be a professional to benefit from this important step when decorating your own home. I'm not even much of an artist, and I have drafted many rooms by hand. Here are a few steps to help you on your way to having a functional and perfectly decorated home:
1. Measure your rooms.
2. Do a quick sketch of the entire house/apartment on graph paper, with one square equaling a square foot. (Designers always round down on half feet)
3. Measure your furniture and make square cutouts of each, using graph paper with one square inch equaling a square foot.
Once you have completed this step you can play around with your different pieces in each room until you find the most functional layout for your family. The great thing about this is that you can see if your room is balanced or not before you call the neighbors over to help you move the bookshelves. A few things to keep in mind when deciding on a layout:
1. Balance the furniture. Don't put all the heavy pieces on the same side of the room.
2. Leave at least 36 inches of walking space around the furniture.
3. Balance the surfaces. Try not to put two hard surfaces (bookshelves, desks, tables, etc.) next to each other unless they are vastly different heights. And try not to put soft surfaces (couches, chairs, beds) next to each other without breaking them up with an end table. Exceptions to this rule would be dining rooms or offices, which require many hard surfaces.
I hope that helps you get started! You will also need to pay attention to vertical balancing, but I will get to that later. :)
Here's a little personal tip: when I am making the layout of my own home, I have a list of what I am going to keep in each room. In the study, I keep books, office supplies, art supplies, sewing machine. In the baby's room, toys, crib, changing table, baby clothes, rocking chair, humidifier. This helps me figure out what furniture needs I have for each room, and it helps to organize some of those loose items that don't have an obvious space. When you know the function of each space, you can really work on incorporating it into the overall aesthetic of the room.