Fanfics, if done right can be quite good.  Too bad they usually suck.

Most of them suffer from at least one if not all of these major flaws.

Self insertion - This is the worse of the worse.  this is usually accompanied by describing how much cooler they are than the other characters, and they almost always play a more important role than anyone else.

Character removal - Take a character you dont like, and simply remove him. Often times either killing them off early, or not even bothering to mention them.

Personality changes - OOC (out of character)comments and actions.  some are acceptable, but others are just wrong.  whats worse is when theres a hastily scribble back story to explain why someone does something OOC.  Thats almost admitting that they know what they are doing is wrong.

Background drops - What would Luke Skywalker do when stuck in a Lord of the Rings world?  DOnt know, i dont care.  Too bad that person did.

Romance stories - I really dont need/want the details of what Captain Picard Dr. Crusher and Lt. Troy were doing on their holodeck vacation to Tahiti.

I have tried some fanfiction, and I find it very constricting, due to the fact you must follow someone else's laws and rules, as it is their world.

the greatest problem comes down to some people believeing that if its too hard to work within the rules, ignore the rules.

in proven guilty theres a cheap shot/homage at "aliens" that i though was quite excellent.  Sometimes its best just to have a few trusted friends look over something though its the only way to be sure.

this should be a safe way provide an example, if not, delete it.

story idea: (type of thing you cant do.)

Darth vader needs to go searching for the children while hunting the few remaing jedi.

then he should have to run into trouble from rebling planets, thus running into the need to construct a weapon that can destroy planets.