I'll take the no-tech, no explanation approach. Try the following. Put the camera on Shutter Priority mode (Tv usually) NOT Auto. Set it to 1/90 sec if subjects are still, 1/250 if they are moving around some. Make sure the camera is set to auto adjust ISO. Make sure you are doing your best to focus on the correct thing, and see what happens. If you are perceiving that what you focused on is sharp, but too many objects closer or farther are too soft for your tastes, then change the camera to Aperture Priority (Av) and try setting it at 2.8 and also 3.5, then make sure that the minimum shutter speed in your Auto ISO setting is 1/125 and then see what happens. This is for indoor, no flash shots.