Unless a material is labeled as containing asbestos, you generally cannot tell if asbestos is present simply by looking at it. In the past, asbestos was added to many types of construction materials to strengthen, insulate, fireproof, and soundproof. For this reason, it is difficult to identify for certain if you have asbestos in your home or building without first having the building tested for asbestos contamination.
The EPA suggests that you have your home inspected by a trained and accredited asbestos professional if you suspect you may have asbestos-containing materials in your building.
The EPA also suggests that you schedule an inspection before you begin remodeling or after your home or building experiences damage where building materials have been disturbed. (drywall crumbling, insulation falling apart, etc.)
Below are some images of asbestos-containing material. Keep in mind, the best way to handle any situation where you suspect asbestos may be present is to contact a professional asbestos abatement company or asbestos testing company.