First things first...I don't believe in rules for decorating. There are no real rules except the ones you set for yourself. However, a game plan is always a good idea, and I'll try here to give you some guidelines to get you started on your way!
Trust yourself. You know more about what looks good than you think...it's your home, it's YOUR opinion that matters! Ok, your family might have a little to say. :)
Select the most important element in a room, and make it your focal point. For instance, a fireplace in a room makes a classic focal point, and furnishings and objects are arranged around it.(Don't have a fireplace? Check out the projects page, you could!) Find something to direct your eye to, even a view out a window.
Set a theme for each room. It helps tremendously! You wouldn't write a story without a main idea, would you? Even if your theme is just a color combo that you love, it will give you a starting point and guide you.
Work from the largest area in a room to the smallest when planning your design. For instance, walls, windows, floors, furnishings, accessories. The larger the decorating surface, the more immediate impact it will have.
A word about combining color and pattern. The easiest way to pick color combos that work is to borrow from a piece of the fabric or wallcovering to be used in that room. For instance, let's assume the main fabric in a room is a floral. Use one color from the fabric on the walls, one or two on accessories, you get the idea. Just be sure each color or pattern you use shows up in at least two places in the room. Or, use those magazine photos, and borrow one of your favorite color schemes!
You CAN combine pattern...choose one dominant pattern, then use several different types of less dominant(smaller prints, less brightness,etc...) patterns, with all patterns sharing at least one common color. Be careful, and use only as many patterns as it takes to achieve your look...a room that looks too busy is NOT restful.
Have fun! A big part of the satisfaction in decorating your home yourself is being proud of your creativity! We are ALL creative. Use the ideas in this website, and the online course if you wish, to find the creativity in yourself! Good luck!