Posted this on anohter forum but i though id share it will all of you aswell =]. lol copy and paste ;]
Im doing this because i really enyoy GFx and i love seeing good work. I hate it when good work is ignored for something that isnt actualy that good. It might be one has a render of something popular so people will in so people will instantly say its good without really looking at the sig itself.
This is the things ive found what actualy makes a sig good:
Depth
flow
composition
concept
effects
Text/misc
Ill go over some of theese things in this thread to give you an idea of how you can spot these things out in somones sig. This will also help you give advice on someones sig if they dont have any of the above in it.
Depth: In a sig you should have a main focal point. This is what you will be looking at in the sig most of the time. The main focal point in sigs would usualy be the render you are using. But you can decide it to be something else if it looks good =]. Now you really want ths main focal point to stand out from the sides of your sigs,the background and the effects. So in other words things that are suppose to look further away in you sig should be blurrier make the sig look "Deeper".
Here is a simple example. Ill use my friends sig from another forum to show you
Notice how everyone else other than the main focal is blured, and if you look close the further away they get the blurrier they are. That has added depth to his sig =)
That was quite a simple example but you should get the point. Some ways of adding depth into your sigs are: Blurring and sharpening like i mentioned in the above. But you can also use adjustments and other tools to do this aswell. burn/dodge tools. Creating shadowing with the levels and curves adjustments.
Flow: I find flow a little harder to explain but it pretty much means that the render/effects in you sig seem to all move in a certain direction (flow in a certain direction) The direction of flow would depend on the render you are using. If you have a sig that is facing a certain direction (left or right) i would suggest making it flow in the opposite direction of that sig. but in some case it will work the other way around.
But if the render is facing foward in the sig i like to make my sig go off in two directions with effects. Alot will say that it isnt flowing when you do this but i like to disagree ;]. Heres an example of what i mean
But if you cant make the render flow in one direction when they are facing fowards you could always just make the backgroun flow instead.
Concept: This is just the idea behind the sig. Like this ones concept is death
As you can see they guy who made this sig pulled off the idea really well. Looks like he has just collapsed onto a table has blood running from his mouth blood then running across the glass table. You should really take you time when looking at peoples concepts. Have a look at the render or stock they used and see how much effort really went into the sig.
Effects: Effects really do make a sig great imo. You can do sooo many things to add effects that it just isnt funny. Alot of people tend to use effect c4ds now but effects can also be added by smudging and clipping masks. I would say brushing i think brushes look ugly unless it is a vector sig or you are using a soft brush for lighting.

<- Nice effects =]
Text/misc: Text is something i actualy completley fail at. But usualy try to keep the text simple if your not good at it like me xD. Also when doing text try to make the colours match the sig and blend it in. Notice the text in that last sig that i posted. Afew things that you can add to text to make them kool are: adding clipping masks, gradient maps and strokes.
Other things to take note of: Lighting. You will notice alot of sigs have light sources in there sigs. (the parts that look shiny and glow ;]) You make these by using soft brushes and setting it to scree/linear dodge.

Not the best example but you can see where the lighting is.
Boarders: Dont really like boardesr all that much but try adding a boarder that matches the sig. Some sigs look better without them though.
Hope this helps. Have fun commenting on sigs now ;]