As a student in a general chemistry lab, you must respect the concentrated acids and bases that are in the lab.  All of the acids and bases that are 6 M or higher can eat through your clothing and skin in seconds.

Respect for concentrated acids must also be present when diluting them with water.  A concentrated acid releases a large amount of heat when it undergoes hydration.  Sometimes steam is generated.  Thus,

NEVER POUR WATER INTO A CONCENTRATED ACID.

If you do, the water is unable to absorb the heat generated simply because of the lack of water present.  

NEVER MIX A CONCENTRATED ACID WITH A CONCENTRATED BASE; THE REACTION IS VERY VIOLENT.