If you’re taking pictures of friends or family focus on them first. Bring them in close to your camera and then work on getting what you want in the background. A good rule of thumb is that if you don’t think someone else could tell who is in the photo with a brief glance at your phone then they’re much too far away. I live in Vegas so I see this all the time. Someone will want a photo in front of the Welcome To Vegas sign or the statue of Siegfried & Roy so they’ll back all the way up to the thing they want to be next to but its much larger than they are so to get the whole thing in frame the photographer will also back way up. Next Thing you know the person you’re photographing who is actually the most important thing in the picture is so small you have to tag the photo to identify who it was. Try this. Get the person nice and close and try to put whatever the thing is over their shoulder or beside them. I’ll bet you that you’ll love the result.
Watch out for large differences in the lightest and darkest parts of the photo. Cellphone cameras have have very limited dynamic range which means that the difference from the lightest light to the darkest dark can’t be that much. A classic example of this problem is a beautiful sunset. You want to take a photo of someone in front of that amazing sky. The trouble is that now the sky is almost completely blown out and the person you were photographing is super dark. The traditional photographic solution would be to use a flash but cellphone flashes are pretty weak so you’ll need to handle this a different way. Try facing a different direction.Maybe not a complete 180 but try to get it so that the sun is at least partly lighting your subject from the front which will largely get rid of your problem and help you get a fantastic photo.
Play with the flash… especially during the day. I don’t know of anyone who really likes that “flashed” look and as a professional photographer I do everything I can to prevent my photos from looking like I’ve actually used a flash. The thing is I actually use a flash all the time. Flash can do some amazing things but on a basic level it’ll help you remove the harsh shadows from your subjects faces and it will do wonders if you’re trying to equalize a dark subject against a lighter background. There are two things you should know about flash that will help you hide the fact that you’ve used it. The first and most important is that it’s the same color as sunlight which is far more blue than most indoor lights. If you’re photographing indoors you’re probably out of luck unless you carry color conversion gels but if you can get some sunlight to help you or if you’re photographing outdoors you might be in luck. Flash is amazing in daylight by the way. The second is that the flash on your cellphone will create very hard shadows so try and keep people away from walls or you risk outlining them with a very obvious and very ugly shadow.