It’s great if you want to become an ethical hacker. The world’s connected software is currently not very secure. We need many hackers who will hunt for software vulnerabilities and report them to the owners of the systems.
You need a great dose of curiosity, tenacity, attention to detail and logical thinking. All and any knowledge of how computers and software work will be useful.
Start by creating your own hacker account on HackerOne (Bug Bounty, Vulnerability Coordination). This will give you access to vulnerability disclosure and bug bounty programs on which you can test and hone your skills. As you make progress and improve your hacker score, you will get invited to more demanding bug bounty programs.
To learn, read everything on the topic you can find. Perhaps the greatest learning comes from vulnerability reports submitted by other white hat hackers. You find them on the Hacktivity list (Latest Security Vulnerabilities Found, Rewarded, or Disclosed).
HackerOne also publishes blog postings (Latest Updates and Insights About HackerOne) with tips and techniques for hackers. Many white hats have Twitter accounts and blogs, sharing their learnings with the world. Read and study as much and as often as you can.
A great book to read is Web Hacking 101 by Peter Yaworski (Web Hacking 101 by Peter Yaworski [Leanpub PDF/iPad/Kindle]).
Starting from the first vulnerability report you submit to a company or other organization, you are helping the internet to become more secure.
Happy hacking!
I also recommend the answers here on Quora by a famous hacker: Jobert Abma