One of your biggest concerns in handling evidence at a crime scene should be safety. Find a way to secure evidence while also protecting yourself and others from dangerous objects. Package large, oddly shaped items like machetes in cardboard tubes designed for posters. Place other sharp objects like syringes, knives, and glass fragments in specially designed plastic collection tubes. If any of these items contain blood, other body fluids, tissue, etc., you must mark the outside of the package with a biohazard label.
When dealing with firearms, you must first make sure that the weapon is unloaded, cleared, and safe. The firearm should then be packed in a box specially designed to hold weapons in place. The outside package label must indicate that the weapon has been cleared. If the weapon has blood or tissue, mark the package with a biohazard label. This label is important because it will alert the lab to safety issues and will also indicate that biologic testing needs to be done before ballistic testing. Also remember that the ammunition from firearms should be packaged separately.
From: Evidence Packaging by Dick Warrington