I want to repaint and don't know how to clean walls first. Help!

wash the walls down with a mixture of white vinegar and water, allow to completely dry, use a stain blocking primer by Zinser,allow to dry and then paint

In Australia we have a product called sugar soap which works well. But I would still use a primer first before painting.

Wash them with white vinegar and baking soda.

Try to wash them with dish soap, but don't soak them! Wait until completely dry. Paint with white KILZ. VENTILATION IS NECESSARY! When dry use the color you want and paint over the kilz. This also blocks mold from growing on interior walls ( also great for untreated wood)

A stain blocking primer like Kilz or Zinnser works wonders. You can wash the walls with vinegar. I have also used a heavy cleaner called TSP to clean very soiled walls prior to painting.

I would sand all surfaces with a pole sander, then wipe down the ceiling/walls to remove the dust. I would paint using a primer that contains a sealer and stain blocker, like Kilz. When you go to the store, ask the person in the paint department if this the best way.

I would wash the walls down with Sugar soap or even baking soda before painting.

Wash with TSP.