The warm-up comprises the following elements:
1: mobilise joints 2: warm the body 3: activate core stabilisers 4: light stretching
It may also include conditioning elements. Warm-ups are usuallt 10-12 minutes long; conditioning-focussed warm-ups as preparation for class may be up to 20 minutes.
A video of a sample warm-up, of light to moderate intensity.
And here's a sample warm-up aimed at rapier fencers: