There are other skills plumbers need aside from being able to work with water. One of the most common things that a water leak on is fixing water lines.
There are two, one on each side of the toilet, closet bolts which hold the toilet to the floor. If there are caps over the bolts, remove or pop them open. Using a small crescent wrench unscrew the nuts from the bolts. Alternate side to side when unscrewing this will be much more important when reinstalling the water line repair bolts but alternate anyhow.
In repairing a tub faucet, you will notice that there will be drips that you need to address to. With this, you will need to replace the washers and/or seats.
The next step in this process is to determine what type of method is available for fixing the problem. You cannot just caulk a crack or fill it in with cement and hope for the best. Unfortunately, there is more work than this because you have to fix the problem from both the inside out and the outside in. This takes a professional in most cases to determine the best method for repair.
Check that your plug holes and waste outlets are clear of hair and solidified soap also check the "U" bends or traps under your sinks for potential blockages. Occasionally pour boiling water line repair down your sinks and shower wastes not forgetting the washing machine trap. Look outside too for any weeds or leaves that may be blocking gutters, gully's and waste outlets.
From your own point of view, it is important that the plumber be trustworthy and credible. Ensure the plumber comes with at least two strong references which you can verify. This will help you be more secure and suffer less anxiety.
Find out if the plumber works on a 24 hour basis and, if so, what are the extra charges involved. More important than the costs however are the person's trustworthiness and reputation. After all, he or she will be in your home and around your possessions. You should feel comfortable with their presence and confident that they are honest.