One of the most basic things you can do with color curves is the s-curve. Point-and-shoot camera pictures often come out a bit muted in color. The s-curve is a simple way to make your colors pop a bit while keeping the natural colors of the picture.
If you want to be a bit more bold, you can adjust more on your color curve. The first thing you'll want to do is to make your blacks true black and your whites true white. You'll do this by starting your color curve where the pixels in your histogram start.
Now, I could quit there but there's a slight blue color cast to my photo that makes it look a bit cold. This is when you play with individual color channels.
1) You can cause "damage" to your photo when working with color curves. Always work on a copy of your photo until you are confident in what you are doing.
2) When making your blacks and whites true, you are stretching your tonal information. The downside is that you lose some image detail. You'll notice a comb-like pattern in the histogram meaning you no longer have pixels in the image at some brightness levels. Most of the time this is not noticeable to the naked eye.
3) Remember when flexing your curves that as some areas gain contrast, others will lose it and vice-versa.
Have you played with color curves lately?