Defining your terms is so important on two levels:
1) When you are doing research, make sure that you know how a term is being used in the resources you select AND that your resources are using a correct definition of a term.
2) When you present research, either in a speech or in writing, make sure that you define your term so that your audience know how you are using it and in what context.
If your speech invokes "Christians should" or "should not" for any reason, make sure to include Scripture to back up your point. However, be careful not to pick a single verse out of context. Remember 2 Timothy 2:15!