One screenshot every 60 seconds:

ffmpeg -i VIDEO.mp4 -vf fps=1/60 folder/%03d.jpg

One screenshot every second:

ffmpeg -i VIDEO.mp4 -vf fps=1/1 folder/%03d.jpg

With Quality Settings:

ffmpeg -i VIDEO.mp4 -vf fps=1/1 -qscale 2 folder/%03d.jpg

For making contact sheets, I’d highly recommend mtn.