There are certain people who simply look good in pictures; it seems like, no matter what the circumstances or conditions of the photo shoot, they always manage to cop gleaming poses with radiant smiles: even if they are caught by surprise, in the middle of a downpour, or just getting out of bed. Now, while these people do exist, who can manage to pull off great photos without looking insincere, there also exists their counterpart: those who always look (in a certain sense) good in photos, who are always ready to manufacture an identically perfect smile each time, but who do not look like they mean it at all. There are some people who are so picture-conscious that, if you snapped a photo of them while they were in the middle of fighting off muggers, they would turn to flash that perfect picture smile nonetheless.
This being the case, then if you are neither type of person described above, and you generally do not look good (in either a believable or unbelievable way) in pictures, then when asking yourself how you can change this, how you can make yourself look better in pictures, you must also ask yourself how you can look better in pictures without looking phony and unbelievable. If you are going to shoot for improvement (pun intended) in the world of pictures, then you might as well shoot straight for the top; namely, looking great, and flashing a great smile like you mean it. Here are a few tips that could help you look not only good, but also sincere, in pictures:
1.) Smile. This seems obvious, but bare with me a moment. Saying cheese, or tightening your mouth muscles (or whatever the scientific terminology for the motion of a smile is) is easy: anyone can do that, and this is, of course, the first thing the amateur photographer will demand from his or her victims. However, if you need to be asked to smile, then you are not really smiling; you are saying cheese, or just mechanically curling your face, in a vain attempt to manufacture a better looking photo. A real smile, is not something that is so simple as saying cheese, and it cannot be produced intentionally: it just has to happen, because you actually are at that moment happy or you actually do at that moment find something funny. Since part of our goal, as we said above, was to look good like we mean it, rather than in a phoney or manufactured way, then what better way is there to look like we mean it than by actually meaning it!
2.) Surround yourself with good friends. Smiling, that is, real smiling, is not something as simple or obvious as it first seemed; since it is something that cannot be produced at will, but which must just happen all on its own, then how can we work at copping better smiles in photos? A picture (at least a good one) always captures a moment, rather than creating one. By that logic, all that needs to happen for you to look good in a photo, is for you to be sincerely enjoying yourself in that moment when the picture happens to be snapped. The only way you are going to be sincerely enjoying yourself in the moment, is if you are surrounded by good friends. By good friends, I don't mean friends of convenience: people you surround yourself with regularly for the sake of keeping up the appearance of a healthy social life. By good friends, I mean people you feel at home with, or completely at ease with, and that you honestly do enjoy spending time with. Only in this context, of real and not affected friendship, can you be sincerely happy and having fun in the moment that is captured by the picture.
3) Fire your photographer. As it now stands, if you look bad in photos, this reflects the situation you were in when the photo was taken; furthermore, it reflects your attitude towards the person taking the photo. I don't think there is any way that anyone can produce a nice smile for someone they think is tedious and annoying - like I said above, they could say cheese or curl their face mechanically, but they could never really be smiling when posing for a person they can't stand. In that case, if you look bad in photos, this may not mean only that you are not really enjoying yourself in the situation that the picture captured, but it might also reflect your attitude towards the photographer. For you to really be enjoying yourself, and to really be smiling, you have to like the person who is taking the photo; in order to be comfortable enough not to have to pose or recreate an image of happiness, you have to actually be happy and not so conscious of the picture that is being taken. Like when you are with good friends, when you are being photographed by someone that you actually like and feel comfortable with, you really don't care about your appearance, but are at ease: and this is the only way you can really look good in pictures.
There are a score of other tips about grooming, how to dress, and things like that; but, personally, I wouldn't worry about things like that. All tips like this are telling you how to do is how to fake a good picture. Since we've seen above that the whole point of a good picture is that it is sincere, and not faked, then none of those tips are worth bothering with. I think that, if you truly want to look good in pictures, then you should absolutely not, under any circumstances, force anything. If you aren't enjoying yourself, don't smile! You may not look good in the picture, but maybe that will tell you something important: that you belong somewhere else, somewhere where you are happy enough in the situation itself to not need to force a smile. After all, even if you do completely master the art of forcing a smile, and your "smile" is completely convincing, still your pictures are not going to be good ones - they will only look like good ones.