Download link:
http://www.growlersoftware.com/download.html
1. When you install the program, it'll ask you for your record hotkey. Set it to whatever you'd like here (I use Shift+12). Press it once to start your recording, press that hotkey again when you're done.
2. After you've recorded a video, it will appear in the program's main screen along with any other GunCam files you've made (.gcf). Click the file and choose "Export Video as GIF, JPG, AVI." Click the large arrow in the middle, then in the bottom right click "as AVI."
3. Your video, after a bit of processing, will be saved in the AVI folder and you can delete the .gcf (GunCam File). Generally a 24 FPS video of about 20 minutes comes out to no more than 50 MB, while still having top-notch quality.
Be aware, though: the .gcf file that initially records can be enormous, sometimes as much as 4-5 GB. However, these can be deleted after they are compressed into an AVI format and you never really need more than one at a time.
You can set the framerate to whatever you find maximizes your quality to filesize ratio. StarCraft runs in 24 FPS, so anything above that is superfluous. Anything under 8-10 FPS will be very poor quality.
After a 14 day trial, you will need to redownload the program or you will have a watermark stamped onto all videos after that point.