Depending on the chemical being spilled.
1. if it is ordinary chemival
2. if it is highly reactive chemicals like sodium potassium
----->>NEVER THROW WATER..
just spread soil on it.you may see buckets of soil inside your lab kept for precaution.
3.if it is a fire accidenT
----->>use fire extinguisher
4.if it is leakage of inflammable gas
----->>don't change the present atmospheric condition.i.e.,do not switch on or off the bulbs....do not light a lamb.......open the windows,ventilators and doors so that the gas escapes the room as soon as possible.