A slow motion video of the Bryan's practicing - Bob on the baseline and Mike in the net.
Things to look for:
1 This is a practice drill so Mike is not really attacking these volleys but working them back to Bob so he can practice the drives.

2 Look at the height of Bob's drives over the net - classic doubles shots.

3 Look where Mike is practicing from - middle of the box so he can practice this very important low volley - and look where he puts it.

4 Watch the set up for the volley - early and simple.

Now get out there and do it!