This handbook on plaster craft is a great resource and you can read the entire book online:

http://plaster.com/handbook.html

Acknowlegements
History
Introduction
Working Area and Equipment
Types of Plaster
Types of Mixing Vessels
Mixing Plaster
Additives and Their Preparation
Pouring Plaster
Some Pouring Suggestions
Using Armatures
Fillers Added to Castings
Plaques Requiring Hangers
Excessive Weight In Casing
Setting-Time Control
Care After Casting
Removing Castings from Molds
Repairing New Castings
Hollow Castings
Release Agent
Removing Air Bubbles from Heavy Castings with a Vibrator
Drying Castings
Painting
Paint Mixing Guide
Making Molds
Plastic Molds
Preparation of Model for Rubber Mold
Fins
Rubber
Synthetic Rubber Mold Compound
Applying Natural Latex Rubber
Plaster Back-up for Rubber Molds
Marking Molds
Removing Shell and Mold from Model
Waste Mold
Large Molds with Glass Cloth and Resin
Obtaining a Copyright
Where to Sell Your Product
Buyer’s Guide Section

Thanks for the link. I have just started with plaster so this will help me alot. thanks again