A girl could be a great singer and still be a nerd. All of us are nerds in some way. Unless you are just a dork! There are certain things which you need to know before you make an attempt at dating a nerdy girl.
Doesn't understand your gestures or indirect approaches
Forget those normal ways of approaches, by showing signs like smiling, asking for a pen, or something of that sort. She is so engrossed in her thoughts, that she might never notice your indirect gestures. The only language she understands is a direct one.
Very bad social sense
Yes. If you are too careful to spoil your image, this is an alarm!! Don't approach a nerdy girl at all, 'cause you've no idea when she will laugh out loud in a silent space over a joke she heard two days back. Or when she'll be crying puddles of tears in the memory of her favorite late fiction character.