How can you become ethical in your life?

Ethics refers to taking all consequences of your actions into account, looking at what would be the greater good, and doing things that have the least negative impact on others.

A good start would be to follow the Golden Rule, and treat others in ways which you want treated do unto others what you would like done to you. However, the Golden Rule should be taken within reason. It doesn't mean that every whim you want you will get if you do unto others, nor does it mean if you want bad things done unto you that you should do them to others.