* I never add text as the last thing on a signature, but rather put it in before I start with my adjustment layers (gradient maps, color balance etc). This blends the text a lot better with the signature itself.
* Try mixing different fonts together. It's time consuming but well worth it in the end if you have a great variety of fonts available to you.
* Play around with the colors! If one color looks to flat, try double clicking the layer and put a gradient overlay on it, pick colors that already exist in the signature if you want it to blend in.
* Experiment with the blending options and opacity of the layer.
* Create a new layer under your text and put an interesting brush or something behind it to make the text pop out more. This works especially well if the signature is very bright or very dark.
.. that's just some general things I do when working with text. Most importantly, have fun with it!