That depends on what you have kicking around to take pictures with. However, there are some fundamental ground rules common to all coin imaging, techniques you need to use with every camera be it a smartphone, a point-and-shoot or something more expensive. Thusly: 1) Firm camera mount. You cannot allow the camera to vibrate during the image shooting. This could be as simple as laying an iPhone on a stack of books, lens peeking over the edge, or a tripod, or a dedicated copystand. By far the easiest way to achieve this is to have the camera mounted pointing straight down, on the coin laying on a horizontal surface. 2) Camera lens and coin perfectly square to each other. Coin imagery involves a very small depth of field, and if coin and camera are not nicely parallel, not all of the coin will be in focus. Also, the moment you depart from parallel, perspective distortion - which is pronounced in macro photography - begins misleading the observer as to actual details. 3) Remote or delayed shutter. You cannot be in contact with the camera when the image is triggered. Either use a timer or a remote trigger of some sort. 4) Optimize the distance from the subject. This is far tougher than it may seem, because some cameras cannot be very far from the coin to acquire a pic large enough for evaluation purposes. Some cameras cannot be very close to the coin in order to still achieve focus. Even worse, the closer you get, the more difficult it is to light the subject in a manner that will result in a good pic. Which leads to.... 5) Appropriate lighting for the subject. This, again, might be tougher than it seems. The rules for lighting lustrous silver are different than those for circulated copper, and "whatever you may have laying around" probably won't do the trick. Generally, you want the lighting as close to vertical above the coin's surface as you can manage. 6) There is no "Easy Button." You're going to have to more or less learn photography in order to maximize your results. Those are the basics. Specific techniques differ by camera type, so more accurate information will depend on what you're using to shoot with. Some smartphones, like the aforementioned iPhones, are rather capable coin imagers while others are near-useless. The same applies to point-and-shoots, although they have a wider "sweet spot" for imaging. Generally, the larger the actual imaging sensor in the camera, the larger the "sweet spot." The best photographers use dSLR rigs with dedicated macro lenses, which can be pretty expensive (although it's possible to achieve professional results for well under $500 invested in gear, plus a bunch invested in learning).
"Good", when it comes to coin photography, is a loaded adjective. I have seen a lot of "good", but precious little "good enough". The entire attempt at doing adequate photography of an object for which moving attributes like luster are important, is fraught with difficulty.
I think I take a decent picture and I have but 3 rules - proper lighting a solid mounting, and proper white balance. Oh, and lots of practice! Per Dave's suggestions, everything else I do is wrong. My camera is too close (about 3", but my Canon S150 will focus down to 0.4"), I purposely angle my coins because they show better that way (but only about 5°), and I have no remote shutter switch.
Well thought out hand-made engineering. By the way, the part about proper "white balance" can't be emphasized enough. So-called automatic white balance is a TERRIBLE idea. Shots of any coin with color WILL be off. You need to set the white balance with (duh!) a white card, and LOCK IT DOWN.
A fair percent of https://www.cointalk.com/threads/got-wood.65353/ are my pictures and here is a series of 600+ "guess the grade" I did https://www.cointalk.com/search/2546063/?q=grade&o=date&c[title_only]=1&c[node]=7&c[user][0]=7957
I wouldn't call it "wrong" because you've demonstrated the most important aspect of this - learning what best works with your equipment. If you can get a nice clear, well-lit image with the lens touching the coin, you just go on with your bad self. Some of why I say what I say the way I say it (and I've made the post above dozens of times over the last 10 years) is in the interest of addressing "newbie" questions from folks who have never even tried to shoot a coin image before. First you teach the rule, then if you receive continued attention you teach the exceptions.
If you're handy and creative, building a vertically adjustable stand to mount a camera or smart-phone isn't that difficult. However, there are many such stands on the market now that are quite reasonably priced (e.g., Amazon has them).
I use a USB microscope I got from Amazon for about $50. It means investing a little past what you have on hand, but I think it works 'good enough' to show the details needed to describe a coin. It has the fixed mount, above lighting, remote switch, and then the digital picture you can post online. It can take a wide array of full to up close pictures. Really Close:
I have one of those microscopes. Darn thing is almost TOO close though for a good overview. I'm hit or miss taking pics.
