Get professional advice if you are in any doubt, particularly with walls over 1.5m high and complex or stress carrying structures.
Plan the wall and draw a design; this helps with calculating quantities and makes building quicker.
Get the right tools; spade, concrete mixer, trowel, spirit level, club hammer, 60-120mm bolster chisel, stringline and pointing tool.
A firm foundation is essential
Walls need a concrete foundation three times wider than the thickness of the wall. Its depth should be at least 100mm with the base 300mm below ground level.
For walls over 1m high the foundation base depth should be one third of the height of the wall above ground.
Construction
Single skin walls 100mm thick should not be higher than 1m and need 215mm square piers every 2m.
Walls over one metre high should be double skin construction, with the two skins tied together and should have support pillars at least every 3m.
All walls need provision for expansion and contraction about every 6m.
Protect the top of the wall with copings and pier caps or suitably sized paving slabs.
Bricklaying, Mortar & Joints
Use normal bricklaying techniques including damp proof courses where appropriate.
Mortar should be 1 part masonry cement to 4 parts soft bricklayers sand.
Mix bricks/blocks from different packs to ensure a blend of shades. If using just one pack, select from the top down.
With raised planters and retaining walls, leave some vertical joints un-mortared for drainage.
Raised pools require a waterproof liner and a design that will support the weight of water.