You don't have to be a photographer to take good pictures.
The biggest thing I have seen that immediately degrades the image quality is a fingerprint on the lens. It makes a HUGE difference. Get in the habit of rubbing the lens on your shirt before every use. I'm not kidding, you will notice a huge improvement.
Edit: Something I just thought of, I bought an eyeglass cleaning cloth at Walgreens that I keep with me. Great for wiping off the lens and the screen.
Holding the phone steady is tricky and important. You see guys at sporting events with $10,000 cameras and lenses on a monopod for a reason. Don't expect your phone to perform better. Steady it on your knee, a wall... anything.
The only setting that I've seen that I try to avoid but will improve your indoor pics is to set the exposure to +1. Use only if necessary because it introduces some noise.
Lastly, USE THE FLASH and turn on the lights in the room. This is not going to perform in low light like a dSLR. It's a tiny sensor.
Here is a picture that I think turned out pretty good that's the worst possible situation for a camera. Inside, pointing at a window. I did use +1 exposure and the flash is on.
This is using the panorama function. No adjustment to settings but it's in the best possible situation.