This is a warm-up routine I use before I have a barbell back squat session. There are many different sequences you can put together to make an effective warm-up, but it is incredibly important that you run through something like this before you lift.
Once finished I start to warm up with the empty bar and progress from there.
The sequence runs as so;
60 seconds Assault Bike (or whatever alternative is available – row, ski-erg, run)
15 Swiss ball hamstring curls (hamstrings)
4 squat jumps. Make sure your form is solid on these i.e replicate your actual squat. (hip extension/activation/movement pattern)