Have Basic Qualification
You must have completed your schooling at least to consider plumbing to be your field. Without basic education, becoming a plumber is too daunting task. It might consume your half of life to learn to do the job with required precision. So have your regular education upto grade 10 or even 12.
Mathematics, Blueprint Reading and Plumbing
In your regular education or schooling select subjects of mathematics, plumbing and blueprint reading. They will help you to ease into the field of plumbing. Since the work involves precision and some scientific structure, studying these subjects at school is essential.
Take a Placement
You can contact your local plumbers' union or contractors to earn a placement for a few months. This way you can learn practical skills of the trade before winning jobs yourself. If you are unable to find a proper placement with an agency, look for a contractor that does small jobs on his own. Working with him for sometime is also a help to observe and learn practical skills.
Check Out for Licensing Requirement
While trying to learn skills practically, check out what are requirements for getting a license to work as a plumber. Generally your local council is the awarding agency of the licence, and after you are familiar with the process you can apply to become a licensed plumber.
Get Small Jobs
You can start with getting and doing small plumbing jobs in your neighbourhood or locality. This will give you confidence to do bigger jobs, which you can take gradually as you get yourself immersed into your work. You may then become a part of a larger plumbing company to work on contractual terms.