You should be able to wing it with just EV and ISO control and yes, you do it every time the scene, location or lighting changes. Set your camera to Program Mode.
For simplicity's sake, raise EV if the picture is dark. Lower EV if the picture comes out too bright. Do it in baby steps at a time. Yes, you will take a lot of shots and make a lot of mistakes but in the end, you will get one fabulous shot.
Shoot at lowest ISO all the time for best picture quality but if you notice blur during relatively low light, increase ISO little by little until blur is minimized. Just keep in mind that the higher the ISO, the more grainy the picture becomes.
Now you know!