how do you build a retaining wall?

under about a metre (3 ft), interlocking concrete blocks are very doable yourself. dig a trench, put down and compact a good layer of gravel, and bury the first course partly below ground. spend most of your time getting that first course dead level, everything above it copies its mistakes. the part people skip is drainage. backfill behind the blocks with gravel and run a perforated pipe along the base - it's water pressure that pushes these walls over, not the soil. each course steps back slightly into the slope. anything taller, check your local permit rules first, a lot of places want an engineer involved.