Number-guessing game with a cheat code
Depends on how you want to improve it, there's number of ways to go. For instance:

Procedural vs OO code - Extendability

If you wish to extend your game, add new functionalities, make it one game among many that users can play, you'd better switch from current programming style to more modularized one.

Right now that code is contained within "main" method. It's quite common for first programs, to be like that. It's rather procedural programming - you give the computer instruction after instruction. While easy to follow, it's problematic when you try to expand such code or maintain it. It's also mind-numbing to read, making it hard to modify properly. 

You may want to modularize it somewhat:


group instructions together into procedures / functions
more related procedures into classes
leave in main as few things as you can


This is obviously very short answer to very large topic, but do ask if you're interested. You would then have to model the program using objects.

For me that would be number 1. Even over syntax.

Syntax &amp; Cleaning

Tools help

Intellij IDEA has a menu called Analyze. If you select Inspect code there, you'll notice a few pointers, along with explanation. 

Additionally, there is Checkstyle and FindBugs, they also offer lots of pointers.

Heed earlier advice

Giving credit where it's due, I also completely agree with sje397's comment. Let me quote it here:


  Fix indenting. Fix variable names (firstName isn't holding a first
  name). You don't even need to enter the loop if the answer is 'no' or
  the value us 'cheater'. The | symbol is 'binary or' - you want ||. You
  can use boolean vars to store the results of your calls to equals.
  That's a start :)


Less sparse code

Less empty lines. Your code is very sparse which makes it harder to read.

Initializing many variables need not happen in different lines.

    boolean running, guessed, realInt;
    running = guessed = realInt = true;


Rename number to answer.

It's not just a number, it's a game answer.

Read on String comparison

You're using equals for it. There's also equalsIgnoreCase which in most cases is preferred.

Yoda conditionals?

Some folks don't like Yoda-conditionals. 

"value".equals(variable) -> variable.equals("value"). 

Choose your own flavour.

DRY

Keep your code DRY, that is Don't Repeat Yourself. Often you use same conditions in your flow-control instructions (if, while...). 

Cheat codes

You have two cheat codes. One is to input -5, the other is to answer starting question with "cheater". Both serve same purpose, the game reveals the number. If so, why not collapse to ifs into one? Because the code executed in is the same.

Checking user input

Note: this code is changed using pointers above.


| -> ||
equals -> equalsIgnoreCase
less parens, cut those redundant


You may want to shorten them to functions. This is easy to do in IDE. Select ("yes".equalsIgnoreCase(firstName) || "cheater".equalsIgnoreCase(firstName)) and - if you use Eclipse, press Alt+T, this opens refactoring window. Choose extract method, name your method 'yesOrCheater' and proceed. In Intellij the shortcut is Ctrl+Alt+M.



Then

if (guessed &amp;&amp; ("yes".equalsIgnoreCase(firstName) || "cheater".equalsIgnoreCase(firstName))) {


becomes

if (guessed &amp;&amp; yesOrCheater(firstName)) {


Usability

Here is my game log:

want to play the game? Yes/No: yes
I have chosen a random value
Have a go at guessing it
5
Plsease try again
4
Plsease try again
65

# [some tries later]

Plsease try again
3
I have chosen a random value
Have a go at guessing it
2
[...]
Plsease try again
5
I have chosen a random value
Have a go at guessing it


Firstly... please. If I'm to read that word that often, please, write it well. ;-)

Also, how can I quit? I'm bored, I want to quit.

When I guessed right, don't just skip to next game, let me know it wasn't an error in the code, that I "won". ;-)

Finally, random value is a very broad term. Decimals? Negatives? 1:10? -100 gazillions : 98 gazillions? When I read this, I had unpleasant feeling about it, how long do I need to guess?

Testability

You may want to add tests or verifications that your game progresses as you intend it to. Using assert with JVM flag, or some test library (TestNG over JUnit, my personal preference). But that's also a large topic, perhaps for next time.