Hacking is incredibly educational. You must stop being a user and start acting as an attacker. You need to understand how computers work, how networks interfere, how to create and manipulate Internet traffic and what exactly software does, and hey, if you can program a little bit, it will be a huge advantage.
The trouble alone is that hacking is often illegal. This can be solved by asking permission for the one you are going to hack, but then there is a chance that you accidentally break things.
For those who want to learn to hack, but do not want to break the law, there is a lot of training environments available. And that practice is not only educational but also fun to do.
Here you will find 6 free hacking environments that you can use to learn more about hacking
PentesterLab builds unsafe applications that you can put on your computer and then hack it. Some are relatively easy, others are very difficult. Each application contains an extensive manual with background information and exercises.
Web for Pentesters
This teaches you how web applications (like this site) work and how to bypass their security and steal information.
In Kali Linux you will find Metasploitable and hundreds of other types of tools that you can use for hacking. Each tool has its own purpose, and I strongly recommend you to take a look at the Kali linux distribution if you are unfamiliar with it.
It looks ugly, but the practice applications are very nice. You can download them, but you will not get any clues: you just have to see how you are going to hack your way through the applications. Very frustrating in the beginning, but it also feels good if you then manage to break in.
Hack this site is a very active community focused on learning how to hack. You can do all kinds of missions, from easy to difficult. For example, hack a phone network. In addition, you can learn to bypass certain cryptographic protection, get through captcha or build an IRC bot.
Damn vulnerable web
Damn Vulnerable Web Application is a website that runs on your own computer. It is quite easy to install. You can then practice all types of attacks, such as SQL injection and Cross Site Scripting. You can also choose between different levels of difficulty: the website reacts differently to any difficulty. This is especially good to start with.
Links that you can use: