Color and Texture
One of the hardest things to get good at is rendering any kind of digital 3-D model so it looks realistic or even just more than masses of greyish-colored boxes.. One step in this process (whether you're going for realism or not) is to add color and texture to the surfaces of your model. In 3-D modelling this process is sort of like putting wallpaper on the surface or using the paint bucket in Photoshop.

SketchUp keeps colors and textures in a menu called the Materials Browser (Window > Materials Browser). All you have to do is select a color or texture and drop it on the surface you'd like to fill in. You can edit any of these materials in the Materials Editor. You can even make the texture/color more transparent.

Don't be discouraged if your early models don't look very realistic or are even quite ugly. Keep experimenting with creative ways to adjust colors and textures so things look better. Remember that it is virtually impossible to get anything that looks photo-realistic from 3-D rendering program texture/color libraries.

Importing Your Own Textures
A great function in SketchUp is that you can place images (photos you've edited in Photoshop, for example) like wallpaper on the surfaces of your model. Go to File > Import > Image as texture. Browse to find the image you want to use and choose it. Click on a surface of the model to define the image's origin point. Drag until the image is the size you'd like. Release the mouse. The picture is now like wallpaper on the surface. If you scaled the picture to be smaller than the surface, you'll notice that it's "tiled" across the surface. Want to change the position of the wallpaper? Right click on the wallpaper and choose texture > position. See how you can see a giant, tiled wallpaper? Move it around/scale/rotate/etc. 'til it's right and then right click again (choose "done").

You can also create a texture in the textures library (using the Materials editor) with an image in it.

[After adding images as textures.]

Shadows
So even with the new colors and textures, your model just doesn't look right. What you need are shadows. This is one of the best parts of making a 3-D model digitally -- you can play around with shadows to your heart's content.

Make sure the shadows window is open (Window > Shadow Settings). Set the date, time, etc. Click the box in the shadows dialogue that says "Display shadows." Ta-da! Shadows!

[Click on the Shadow Dialogue icon to get this window where you can turn shadows off and on.]

Having shadows turned on will usually significantly slow your computer's response time as you orbit or try to manipulate your model. This is because SketchUp has to rerender everytime you move around (think about how much information has to be processed to create the shadows). Keep shadows turned off unless you're testing out an idea or getting ready to create your final views for a vignette.