Hmmm, OK, be a little careful when asking this, this question is fairly common here and can end up with you getting flamed and told to search the forums.
Anyway, what Id suggest is that you do the following:
- Get familiar with Linux. Check the Linux noob thread and read from the most recent post backwards.
- Then start following tutorials on stuff that interests you. There's lots on this forum, and elsewhere on the web. Reading around generally here will give you an idea of the high level specialty areas (e.g. wireless testing, web testing, software exploitation, etc), and you can focus in from there.
- Then once you are comfortable with the tutorials, start reading books and articles and so forth to expand your knowledge, and try out the things you learn
- Take some training/education if you can (University, Technical College, Professional training like the Offensive Security stuff)
Basically find stuff that interests you and go from there. Also have a look round the forums for similar threads and take note of the advice given there too.
Id also recommend reading the following to get your mindset right. People who do this type of work successfully often think in a very particular way, and it will help you to no end if you can think this way as well.
How To Ask Questions The Smart Way
How To Become A Hacker