Select the girl you want to dance with
If you are at a party by yourself, the first thing you will most probably look to do is select the right girl to dance with. If you know some girls at the party, it would be more comfortable for you to ask one of them, because communicating with them will be a lot easier as compared to asking a random girl. However, if you are looking for an interesting encounter with a girl you have never met before, then feel free to ask any girl who happens to attract or interest you.
Observe her body language
Before walking up to her, it is essential that you pause for a second and observe her body language. At times, your instinct alone will tell you whether the girl will be interested in dancing with you or not. It is also extremely important for you to find out if she is alone or waiting for someone else - all this can be gauged simply by observing the girl's body language. Make sure you do not walk up to a girl who is already with someone - this scenario might end in an unpleasant argument or fight. In short, make sure you observe her and make a couple of intelligent assessments before approaching her.
Think about what you are going to say
It is crucial for you to think about what you are going to say to her, and then practice it multiple times beforehand, in order to avoid an embarrassing situation. However, it is equally important that you sound natural and fluent when talking to her. Be sophisticated in your expression, and do not give her the impression that you are desperate to dance with her.
Have a smile on your face when you ask
If the girl is alone, you can casually walk up to her with a smile on your face, and ask her whether she would like to dance. You should deliver the line with a natural fluency and complement it with positive and confident body language, and a warm smile. If she says ‘yes’, politely escort her onto the dance floor, and enjoy the rest of the party with her.