When designing your home, patience is key. Taking time to really decide what elements to put in each room really will make your house feel like home. You will need to think about your style (what makes you happy? what colors and shapes speak to you? are you traditonal or more modern?), you will need to consider your lifestyle (do you have kids or pets? Do you love to host parties? or have a quite place to read?), and you will also need to think about the functionality of each room (do you want a cozy family style living room for having movie nights? or a more dressy living room for serving cocktail?)
Once you come up with a plan for your home is when the decorating really begins. I think the best designs incorporate old elements with new elements. Even if your style is really modern, try looking for some cool vintage pieces that fit in with your modern elements. The last thing you want is for your home to look like it was all purchased straight from a catalog in one afternoon.
Mixing old and new items is what adds a personality to your home. It will make things more interesting. There are many ways to do this too. It can be as simple as using an antique pieces of furniture or accessories. Or your style might be more fit to take an antique chair and recover it in modern fabric, or refinish an old dresser... this method would give you fresh colors and pattern but you would retain the older style at the same time.
Remember though, finding old, unique pieces takes time. You cant run right out to the mall and find the perfect old wing chair in an afternoon. So be on the hunt when you have the time, know what items you want so that you can be looking for them and spot them, and be patient in your search.