There are many tutorials on the net.
A script can be as simply as executing the same commands you type on the screen:
who am i
For example would tell you information about your current login. Which directory you're sitting in and which directories will be searched when you type a command.
So say you wanted to do something like determine if a specific process (say "fred" was running).
Your script could be as simple as:
However since "fred" appears in the process table as an argument to the command "grep" (the one you just piped into) you might want to augment it by telling it NOT to show any line containing the word "grep":
ps -ef |grep fred |grep -v grep
Check out one of the tutorials as they'll walk you through doing scripts - just remember at their basic form they can simply be a set of commands in a file that you might have otherwise typed at command line. They can get much more complex than that but there is no reason not to start doing basic things and add or modify as you learn.