The most effective way of determining if an electrical wire is hot is to test it with a voltometer. This is a device that measures the presence and power of an electric current. To ensure that an electric wire is not hot, disconnect the power supply for the wire.
Before starting any project that involves electricity, it is extremely important to disconnect the item from the power source first. If you are uncertain or feel unsafe about undertaking the project, call a professional electrician. Never test wires for the presence of electric current by striking them together or on any surface.