Guidance for changing cartridge on my Technis TT

When the headshell is loose gently pull it away from the end of the arm.

By the time you've done that you'll hopefully have remembered the rest of the procedure 

Fatmangolf wrote: If you get other cartridges and mount them on separate headshells as David suggests, I recommend writing down the tracking force and anti-skate settings for each.

This is very important. Also because carts and headshells and styli do not all weigh the same, one has to zero out the VTF before calibrating the new cart. That can be done the old school way or with a digital scale. It's especially important with delicate higher compliance cartridges as applying too much VTF with those, even for a short moment, can risk suspension collapse.

What I typically do is lock the tonearm, back the VTF way off, then remove the existing headshell. I then install the other headshell with cart, then recalibrate VTF with AS at zero. I add the AS last.