There are companies that sell "zero g" rides, where the aircraft is configured specifically to take people and possibly experiments through a parabolic dive to experience a short period of micro-gravity (possibly not the proper term).
This question asks about possible risks associated with the maneuver.
I'm interested in what specific techniques, tools, or instruments are in the cockpit that allow the pilots to properly follow the proper trajectory, while not pounding the occupants against the walls of the aircraft?
A G meter seems pretty obvious, but are there other less common things used? Are there special techniques for managing energy buildup, or for reminding the pilot when to pull out of the dive so as not to over-stress the air-frame?
Any other interesting information that I may not be thinking of in a similar vein is also welcome.