[header] How to clean plaster walls [title] Use the dust brush attachment on your vacuum. [step] Attach the dust brush to the end of your vacuum and run the vacuum over the wall. This is the least abrasive way to clean walls and should always be your first step. 
If you find that your walls are sufficiently clean after using the vacuum, you should stop after performing this step. [substeps] Do not put pressure on the wall as you vacuum it.