I cant really explain it, but i can show you, do you mind sending me your .psd?
Edit:
Well actually..I can tell you a bit
Theres several concepts to text
-Placement, it should be near your focal so the viewer's eyes don't look away from it
-Font Choice, depending on your sig, your font should compliment the theme of your sig.
-Font Colour, theres 2 choices to this, you can either chose a colour that contrasts with the main colour of your sig or a colour that is close to the main colour of your sig (kinda shakey with the words, but meh)
-Effects, there are many ways to do this, its sort of like adding accessories to your text to make it look better/more appealing
-Font Size, ill let rek explain this one

Key points:
-EDGE TEXT IS BAD UNLESS YOU MAKE IT LOOK GOOD (refer to some of rek's sigs)
-NEVER NEVER NEVER PUT TEXT IN A CORNER OR SATAN WILL CONSUME YOUR SOUL.