One of the best parts of having external flashes is using bounce flash. Bounce light of the ceiling when you can. The effectiveness of a flash depends on how the light is able to spread. If you are too close it cannot spread and creates a washed out look, as if you had been staring at the sun and then tried to look at something else right after. I have spent hours playing around with flash and I've learned a few things. For subjects that are close, avoid directly pointing the flash at the subject, unless the ceiling is too high. If you have the ability to use your flash off camera that is even better. You are lucky since you have two flash guns, which gives you a lot of light power to counter shadows.
If possible use some kind of diffusion device. I'm not sure if Canon flashes come with a diffuser or not, but if you don't have one they are not very expensive to buy. Using a flash with reflective objects is tricky, but can be done. Also use flash exposure compensation as needed, the camera doesn't always get it right. When using a flash remember that lower ISOs work great for some things, while not so much for others. If you want some natural light in your shot, shoot at ISO400.
If I had taken the above shot with direct flash the glass would have reflected a lot of the light and been washed out. To overcome that I took an old box that I had lying around the house, and glued white paper into it, placed the subject in the box and took a number of shots, using my SB-800 in remote mode, off camera. A light box allows you to use the light of your flash without having to directly point the flash at your subject.