I think my Nord is a little bit too beautiful for her own good, but she's not exactly flawless, with a long scar across her cheek...

My advice: first, beauty is more interesting if it isn't flawless. I gave my Nord that scar so she wouldn't be too good-looking, but I actually think it had the opposite effect.

(PS3 so no screenshots, sorry... )
Second, go over the presets of the race you choose (if you want flawless, I recommend Nord since they seem to have the smoothest complexion - disclaimer for not having checked out the Redguards since I've never made a Redguard). Remove all scars, dirt, warpaint and strange hairstyles and set the complexion slider to the left. Now you see what they originally look like, and take your pick from there.
Then you can start play around with the sliders, but make sure to memorize (or take pictures if necessary) where they were in the beginning, if you do something wrong and want to change it back. Oh, and set the screen to the brightest, to get rid of as much shadows as possible while you work with the face. Just make sure to change the setting back before you choose skin color.
Take pictures of all the sliders when you're done. Makes it easier if you just want to change some minor detail.