A lot of people (inc. media) are going to start browsing jam sites. There are a LOT of games made. People don't have time to play each and every game, so a great video will drag in the players.
Once your game is finished (or mostly so), it's a great idea to create a gameplay video. This lets other people get a quick overview of what your game is like, especially when there are thousands of different games to review.
Step 1: Recording your Gameplay
The quality of video that you make is up to you. Any of these options would be fine:
(easiest) Use your phone or digital camera to record over the shoulder of someone else playing
Some game tools (such as Unity) have built-in ability to capture gameplay, and you can add script text along the bottom for more info. More info here and here.
For Macs, QuickTime player in OSX can record gameplay. More info here
Anything else you want!
Step 2: Editing your Gameplay Footage
You probably want your video to be short and punchy (the internet does not have a long attention span), to achiever this you'll want to cut the fluff, add a title, credits, music (because you didn't have time to add any to your ggj game), etc.
If you just want to trim the Start/End of your video it can be done after uploading with youtube.
OSX - iMovie is pretty amazing, and simple to use.
Videos should be uploaded to a site such as http://youtube.com or http://vimeo.com.
In the description box:
- Be sure to mention which jam site you're with;
- Include a link back to your game's page at globalgamejam.org;
- Please also add tags #globalgamejam and #ggj20.
On your game's page on the GGJ site, you can add a link to the video in the URL box, and it'll show up easily during game searches.