When it comes to helping to promote your game online on any platform, at any stage, few things are as effective as the humble GIF. They let you snag the attention of a potential player and show off how your game looks in motion, which can get things across a lot better than still imagery for many titles.
Of course, making a GIF, and making a GOOD GIF, are sadly two entirely different things. Luckily for all of us, all you need for the latter is time and practice... and maybe some tips from yours truly that will hopefully help you out. You see, I, too, once stank at GIFs. I would show you the horrifying wreckage of my earlier attempts, but I've locked those far away in a brooding Victorian manor on a hill permanently lit by dramatic lighting flashes.
None of this is to say I am now a GIFing master. But after bumbling along and pushing my own boulder of self improvement up the proverbial mountain, here's what I've learned along the way.
You Don't Need Fancy Tools
There are a lot of expensive, complicated image editing programs out there, but in most cases, the free tools you'll find will get the job done for you just fine. I like to use ScreentoGIF. It's an itty-bitty download that lets you capture all or a specific portion of your screen, with some basic tools to cut out frames, tweak the framerate, and so forth. There are also online tools like the seemingly omnipresent Giphy, or Imgur, which allows you to make GIFs out of videos you upload to the site, or post elsewhere online. Each tool has its own set of pros and cons, so look around and see what works best for you.
It's About Framing
Dead space is dead boring, and it can eat into your file size as well. While you don't need to go as far as cropping out everything but the characters onscreen, just like in any other visual medium, having a ton of dead space is unnecessary and distracting. This goes double if your GIF takes place somewhere with a relatively simple or static background. Consider using a tool that lets you manually select the area you're capturing, so that you're really focusing on the meat of it.
Keep it Short and Sweet
Just because you can make GIFs that encompass a lot of gameplay in a single go doesn't necessarily mean you should. The very best GIFs pack a lot of punch into showing off just a few seconds of gameplay. It allows the viewer to process what's happening quicker than if you smooshed a ton of action into it. Assume you only have a few seconds to capture someone's attention. So rather than trying to make a GIF out of an entire fight, focus on your main character pulling off a really sweet special attack, or your bad guy kicking the party through a wall.
Loops Are Awesome, Done Right
A good looping GIF is hard to pull off for certain games or scenes, and by no means completely necessary, but if you can make it happen, it's kind of like turning up a little nugget of gold in your pan. Seamlessly looping GIFs are very pleasing to the eye, but there are a few things you might want to avoid. Very short loops can get annoying, for example, and loops that try to fake being seamless but are very obviously off by a few frames can be visually jarring. How do you avoid this? Simple... practice and experimentation!
Keep That Quality Criiiiiisp
If you're really married to the idea of GIFing a long or complex scene that balloons it over the filesize that Twitter allows (a meager 15MB as of this writing), then you might be tempted to compress the heck out of it to make it happen, or dial back the quality. While there's nothing wrong with tweaking the framerate or using a compression tool to squeeze out some extra MBs, if the end result shows significant degradation or anything that is a departure from the original game's quality, you might want to reconsider using it to represent all your hard work.
Bugs Are Great
It might sound counter-intuitive, but don't be afraid to show off those "game development gone wrong" moments. A lot of creators seem to think they should only show off footage that is perfect and shiny and wonderful, when showing off those bizarre and weird glitches is just as fun for the players. Did your character's head glitch into an unspeakable eldritch horror? Did their feet suddenly turn into bunny rabbit sprites? Sharing that isn't just a fun way to interact with your community, it can help lessen the frustration of glitches for you by turning them into something to laugh about.
Variety is Key
If you have people who already follow your game and engage with it, one way to thank or reward them (and people who just might simply be mildly interested) is to choose GIFs that show off things from your game that aren't already depicted on your website, press kit, trailer, etc. You can pique someone's interest by showing a snippet that showcases a character, location, or technique that won't show up until later. It may seem relatively minor, and you don't want to give everything away, but small things like this can keep people invested in your work coming back for more.
Practice, Practice, Practice
In the end, the most helpful tip to make great GIFs is one nobody really wants to hear, but it's one I'm still doing myself. There is no "one magic trick" to make solid gold right off the bat. The more GIFs you make, the better you'll get at it, and that's just the truth. You'll develop an eye for what works and what doesn't, what once took you an hour will take fifteen minutes... you get the picture. So don't get discouraged, and don't let feeling like your GIFs aren't quite perfect yet keep you from sharing them and refining your skills.