When I hear the word modern, I think about crisp, clean lines, big open spaces and lots of neutral colors. At least, this is my impression of what modern home decor means, but it is great that you can find a basic guide to modern decorating by simply doing an online search.
But ultimately, there is so much more to the modern home decor theme than meets the eye. The underlying theme of the modernist style is getting the most functionality in any room of your house. Instead of filling up every inch with bric-a-brac, modern stylists want uncluttered spaces to help relax the eye and give freedom of movement.
Lighting is also an important element of the modern home. Instead of using smallish lamps and light fixtures, opt for bright white lighting or big windows that let in natural light from the outside. Look for sleek and shiny lighting fixtures instead of, say, crystal chandeliers to adorn a room.
For the walls, you can pick classic white or any other neutral hue such as gray, off-white or beige. This lets the eye focus on each of the decorative items in the room. Finally, go for furniture that has mostly crisp lines such as a straight-backed couch. Liven up the look by choosing more colorful items to accessorize the room.