Okay. What the heck is all this talk I hear about Power Gaming/God Mode/God Moding?

 All of those terms pretty much represent a single, solitary thing. Taking an action involving another character that isn't yours without permission. Be it a body movement, facial expression or thought. 

 Whaa-? I don't understand. 

Okay, let's try and explain. I'll assume that you've got your basics of role-playing down, such as actions, thoughts and speech, right? And let's assume that you've role-played a little bit. 

Now, let's bring in our cast of characters who will role-play for us and help us explain.

Judy - Judy's a fun loving witch who likes to kick butt, chew bubble gum and shop. 

Jake's a fun loving easy going guy who just wants a beer.

These two players have never met before and have had no prior communication out of character.  

The setting: A Tavern!

 ::Jake walks up the porch steps and goes to open the door.:: 

::Judy sees Jake, walks up to him and punches him in the face.::

Okay. I don't see anything wrong with that?

Whoa, whoa, hold on there champ. Judy just walked right up to Jake and punched him in the face? What if Jake has super fast reactions and dodged? What if Jake ducked? What if Jake turns into a man-eating wildebeast when he gets punched? What if Jake's nine feet tall and Judy's only five? What if Jake's player didn't want his character to get punched? 

Alright, I get it. Judy didn't give Jake's player any room to decide how Jake would react, yeah?

That's correct. What Judy's player did right there is a small but excellent example of power gaming without permission. She didn't give any opening for Jake to decide what his character would do or if he could take the punch or not, nor did she take any time to consider anything else. 

Yeah, but, sometimes in real life we just haul off and do stupid stuff, right? 

Yes, we do. And while a touch of real life is always good in role-play, what we can't fail to forget is that this isn't really real life and some players aren't into having things happen to their characters without knowing beforehand/without granting permission beforehand. So it's really not 'the cool thing' to do. 

What if I ask a player OOCly beforehand and they agree?

If you ask a player out of character beforehand if you can do something to their character and they agree, then it isn't power gaming. It's cooperative role-play! :D

What if Jake does nothing BUT dodge ALL of Judy's attack?

Then it's obvious that Jake doesn't want to play along or have Jake get hurt. You can try to discuss actions with another player out of character that doesn't seem willing to respond; but be aware that having a character harmed or in danger's way isn't everyone's cup of tea. Respecting a fellow player's wishes is one of the main things which make up the backbone of cooperative freeform role-playing. If they don't want it to happen, what can you do? You shouldn't force them, just like you wouldn't want them forcing it on you!

Huh. I think I get it. Can you give me some more examples of what power gaming is? 

Gosh, I thought you'd never ask!

• Reading a character's thoughts without permission. It's not a practice many role-players like. If your character is telepathic/empathic, try your best to ask permission of other role-players if it's alright if their character picks up on thoughts or emotions. 
  
• Telling another character how he or she will react.
  
• Dictating how much damage a character will take from your character's attack before the other character acknowledges it.
  

Hold up--What's this 'Telling another character how he or she will react?'

Let's bring out Jake and Judy!

::Jake dodges, reaching up to flail wildly. :: What was that for?!

::Judy smiles, watching the fear finally cross Jakes eyes and then smiles wider watching him fall to his knees before her in terror.:: Because!

Do you see the part where Judy writes Jake as being afraid and falling to his knees, when Jake's character didn't? Yep, that's a part of power gaming too. Again: What if Jake's not afraid at all? What if Jake wanted to start doing the two-step, and not fall to his knees? Judy's calling the shots here and that's not fair to Jake!

I hope that helps shed some light on your journey in role playing. Good luck and happy gaming!