What is the best way to build a sleeper/retatining wall approximately 1.8m high in sandy conditions?

Answer 1

My guess would be to make sure your footing is adequete, also use landscape mesh.
( geosynthetic reinforcement mesh)
Open link below for small photo of the mesh.
http://www.geosyntheticproducts.com/geogrid__.html
scroll down to
sleeper walls
http://www.cobblepatch.com.au/diy/retaining_wall.html

Answer 2

You might check out some of the do-it-yourself sites also. Here are a few which have instructions:

http://www.doityourself.com/stry/buildretainingwall
http://www.lowes.com/lowes/lkn?action=howTo&p=Build/BlkRetWall.html

Here's some mention of working a wall on sand:
"Loose, sandy or exceptionally wet soils, for example, will require wall footings to extend down deeply and be wide enough to deal with unstable soil conditions."
http://ideas.reliableremodeler.com/Article.aspx?ID=883
http://en.allexperts.com/q/Lawns-725/Landscape-retaining-wall.htm

*~ Good luck ~*