Without more information about you it's hard to really say. As an example - what are you interested in? Do you like hardware? I got in to kernel development by

Without more information about you it's hard to really say. As an example - what are you interested in? Do you like hardware? I got in to kernel development by basically being the only person willing to do it when it was needed. But I'd already done a heap of kernel work as side projects, and was already working as an embedded developer. I know some people get in to security by breaking systems, but I don't know enough to say any more.