Let the people in your house know that you've organised a plumber. This lets them know there'll be a tradesman in the house and it also lets them know your fixing the plumbing issue 

If you have a water leak that could cause damage to your home then the best thing to do is to turn off your water at your water meter (Usually located at the front of your home) to stop the spread of water throughout your home.

If your problem is outside in the rear yard, organise any pets that don't like strangers into a place where they feel safe (The garage or another room in the house where they're not going to feel threatened)

If your problem is under a cupboard (Vanity or kitchen sink) now could be great opportunity to show your cupboards some love and clean out any belongings before we arrive

If we will need access through a side gate or garage that hasn't been opened in a while - nows a great time to locate the keys if necessary

Most importantly you can now relax, you've done the right thing by calling a professional plumber. Your plumbing issue will be fixed very soon