Your order may vary:
First, think about the condition you want to change. Make sure it is actually a problem and isn't just something you can fix by yourself.
Second, Ok, you can't fix it yourself. Go to the management, thats what they are there for. If its a specific policy you have a problem with at least try the discussion route.
Third, if your immediate boss doesn't do anything about it; go up the chain of command. Take it as far as you can. Maybe someone else will listen to you.
Fourth, Ok, if that doesn't work; then go to your fellow employees. Discuss the problem with them. They might be having it to. Then, go together to management with your concerns. Maybe make a petition and get people to sign it (not just employees, you can get customers on it too).
Fifth, go to agencies outside your workplace. For instance, in the US you can go to OSHA (Occupational Safety and Health Administration) or to the NLRB (National Labor Relations Board); or a variety of State government offices.
Sixth, if all this still doesn't work, its time to Fire Your Boss.
Direct action gets the goods.
Seventh, and if you still can't get your conditions improved, its time to form a union.