Making a garden wall?

Firstly check with your local council as regards footings depths,in most areas it's 2'.A 600mm wide foundation with a 2x12mm steel reinforced bars running the length of the foundation would do in most cases as your wall will only be 225mm wide and centre the wall itself in the foundation.I wouldn't go laying brick below ground level I would use concrete block(440x215x100mm) and lay the on flat to bring me back up near ground level maybe 75mm or 1 brick below and start my brickwork there as for styles or bonding every client is different and it's they who determine what they want,start you wall in 1 corner and build toward the other end of the wall don't ever build 2 corners first and run it in as you could end up with a piece in the wall which isn't good as for mixing 4:1 sand and cement for the mortar and depending on the wall I'd always use a mixer it's way faster as for the stone same thing build up your block work first and then start just below the ground with the stone but in some cases the foundation has to be wider than 600mm as a lot of stone walls are wider than 225mm and your footing width has to be widened to suit ok,good luck.