There are so many way to hack.
Generally speaking, there are 11 steps to hack a computer.
1. Learn a programming language. You shouldn't limit yourself to any particular language. C is the language the systems are built in, it teaches you what's very important in hacking: how the memory really works. Python or Ruby are modern, powerful scripting languages, that can be used to automatize various tasks; Perl is a good choice in this field as well. PHP is worth learning only because it's what newbies use to "hack" poorly written web-applications (forums, blogs etc). Bash scripting is a must, that's how you can easily manipulate most servers - writing one-line scripts, which will do most of the job. Finally, you can't do much without knowledge of ASM - you *can't* exploit a program if you don't know that.
2. Use a *nix terminal for commands. Cygwin will help emulate this for Windows users. DOS is worthless in this area. The tools in this article can be found for Windows based machines. Nmap particularly, uses WinPCap to run on Windows and does not require Cygwin. However, Nmap works poorly on Windows systems due to the lack of raw sockets. You should also consider using Linux or BSD, which are both more flexible, more reliable, and more secure. Most Linux distributions come with many useful tools pre-installed.
3. Try securing your machine first. Make sure you fully understood all common techniques, including the way to protect yourself. Start with basics - found a server which has site about racism, homophobia or other bad activities? Try to hack it, any way you can. Yet again, don't change the site, just make it yours.
4.
Know your target. The process of gathering information about your target is known as 'enumeration'. Can you reach the remote system? You can use the ping utility (which is included in most operating systems) to see if the target is 'alive', however, you can not always trust the results of the ping utility, as it relies on the ICMP protocol, which can be easily shut off by paranoid system administrators.
5. Determine the operating system (OS). This is important because how can you gain access to a system if you don't know what the system is? This step involves running a scan of the ports. Try pOf, or nmap to run a port scan. This will show you the ports that are open on the machine, the OS, and can even tell you what type of firewall or router they are using so you can plan a course of action. You can activate OS detection in nmap by using the -O switch.
6. Find some path or open port in the system. Common ports such as FTP (21) and HTTP (80) are often well protected, and possibly only vulnerable to exploits yet to be discovered. Try other TCP and UDP ports that may have been forgotten, such as Telnet and various UDP ports left open for LAN gaming. An open port 22 is usually evidence of an SSH (secure shell) service running on the target, which can sometimes be bruteforced.
7.
Crack the password or authentication process. There are several methods for cracking a password, including brute force. Using brute force on a password is an effort to try every possible password contained within a pre-defined dictionary of brute force software. Users are often discouraged from using weak passwords, so brute force may take a lot of time. These days there are major improvenments in brute-force techniques. Most hashing algorithms are found weak, and you can significally improve the cracking speed by exploiting these weaknesses (like you can cut the MD5 algorithm in 1/4, which will give huge speed boost). Also new techniques use graphic card like the processor - and it's thousands times faster. You may try using Rainbow Tables for fastest password cracking. Notice that password cracking is good technique only if you already got the hash of password. Trying every possible password while logging to remote machine is not a good idea, as it's easily detected by intrusion detection systems, pollute system logs and may take years to complete. It's often much easier to find other way into system, than cracking password.
8. Get super user (root) privileges. Try to get root privileges if targeting a *nix machine, or administrator privileges if taking Windows systems. Most information that will be of vital interest is protected and you need a certain level of authentication to get it. To see all the files on a computer you need super user privileges. This is a user account that is given the same privileges as the "root" user in Linux and BSD operating systems. For routers this is the "admin" account by default (unless it has been changed), for Windows, this is the Administrator account, etc. Just because you have gained access to a connection doesn't mean you can access everything. Only a super user, the administrator account, or the root account can do this.
9. Use various tricks. Often to gain super user status you have use tactics such as creating a "buffer overf