Here's how to remove old plaster when starting a remodeling project. Have professionals remove any old electrical connections and gas piping. Wear eye protection, mask, and gloves. First, remove the plaster using a flat bar, then remove the old lath with a hammer. Haul out the plaster and bundle up the lath for efficient disposal.
For more on plaster, consider:
Skim Coat Plastering
How To: Rebuild a Wall with Three-Coat Plaster
Blueboard and Veneer Plaster Offer Old-Style Look