Writing "Please ___" is a formal way to ask a question. You can use "Please ___":

• for very important requests
• when you are angry at someone and don't want to be too friendly with them
• when you're writing to someone who you don't know
• when you're writing or making an announcement to a group of people

For a friendlier, but still very polite, way to make a request, you can write:

If you could get back to me by the end of the day, that would be appreciated.