If you're on Windows and using a Wacom tablet for drawing, I highly recommend using this plugin. It does a great job at smoothing out those pen strokes - something that Photoshop really struggles with. Has a free trial. Apparently a Mac OS version is on it's way.
Hey Stuffy, thanks! I recently found out about this too.
For linework, I'd really highly recommend using different software all together. Try Manga Studio. It's like Photoshop but just for the things that you want. It might take a day to get used to, but the brushes are far, far superior for the type of stuff that we do.
I found out about Lazy Nezumi when I was trying to get PS to act more like MS. Even with the plugin enabled, it was still nowhere near as good.