I'm far from an expert on photography, but I'm slowly learning things from the pro. One thing that has made a huge difference is adjusting the white balance. It's really easy to do and makes a big difference. You just go to your menu and scroll to the area where I have it highlighted. In this case it's a sun. (yours may be set on one of the other settings that you see in the second picture) Click on that setting to change it.
Once you're in the white balance menu you'll be able to select the environment you're in for the best white balance possible. There is an auto setting which will work most of the time, but I find it better to choose the specific setting I want. Below you can see daylight is selected, you could also select shade, tungsten lighting, outdoor, etc.
Here's an example of what a difference this makes. This first picture is taken with the white balance setting on daylight which is obviously wrong for this room since it's indoors with no windows.
Then I changed it to Tungsten Lighting and look what a difference it made!
I have a cannon rebel T1i, but I'm guessing the process would be similar on other cameras.