Maybe I'm old fashioned, but I mount my moulds to the hinge is away from me, and the extension that gets used to open the sprue plate is facing toward the hinge of the handles. This is how H&G mounted their moulds (as shown in their manual). I like to open my moulds with a gloved hand rather than using a mallet, but occasionally I need to use a mallet if the mould isn't up to the proper casting temp.
The nice thing about moulds that have removable handles is that you can mount them either way, and they're both the right way to do it!
For moulds that have lots of cavities (more than 4) I really like using a cam lever mounted to the sprue plate. This is one of the things that Lee really did right! I have cam levers mounted on a couple of Lyman 4 cavity moulds, as well as one mounted on a SAECO 8 cavity mould (these are levers made from plate steel, not the Lee sintered ones), and they really do make it easy to open the mould.