WHERE and HOW TO START HACKING ?

After you get yourself a good scanner, scan some prefixes and find some cool dialups, then do the following:
First Method:
From your terminal, dial the number you found.
You will hear a series of Beeps. (Telling you that you are connecting to a remote computer.
After few seconds you will hear something like "CONNECT 9600".
It then identifies the system you are on.
If nothing happens after it says "CONNECT 9600" try hitting ENTER a number of times.

If you get a bunch of garbage adjust your parity, data bits, stop bits etc. until it becomes clear.
Now when you get connected to the server you can apply either of the above mentioned methods.
Second Method: The TELNET way
Get your local dialups.
Then you dial the number from your terminal & connect.
Press Enter and wait for a few seconds.
Then it will say "Terminal =".
Type your terminal emulation.
If you don't know what it is hit ENTER.
It will give you a prompt @.
Type 'c'(connects to the host)
Type NAU (Network user address) that you want to connect.
Find out the type of system you are on UNIX, VAX/VSM, PRIME.
Here is a list of some Telenet commands and their functions.
c Connect to a host.
stat Shows network port.
Full Network echo.
half Terminal echo.
Telemail Mail. (need ID and password)
mail Mail. (need ID and password)
set Select PAD parameters
cont Continue.
d Disconnect.
hangup Hangs up.
access Telenet account. (ID and password)