Ok so first off my first tip is good outside lighting! nothing worse than inside blurry crappy lighting that makes you look like a ghost. As you can see here the picture on the right of me looks much worse than the picture on the left! Natural lighting is great however remember where the sun is when outside you want the sun pointing at you not behind you. This is what gives me that glow like radiant look that makes my skin look great.
Don't fake pose, whatever you do try and do something you do naturally because otherwise it will come off fake. Don't pout if you don't pout normally, don't do the cheesy grin if you don't do it comfortably.
Find your best angle! I take a lot of selfies just to gather my best angle I have found I look best from a slightly turned angle rather than front on. However if I take a shot front on I make it slightly lower than my face height as it elongates my round face. Start by taking pics front on, and then slowly turning your face at different angles until you find your best angle that you agree with.
Hope these tips have helped!