A party can be the perfect place to practice your photography skills. It will offer you the chance to photograph people eating, drinking, laughing, talking, dancing… so you will get lots of practice photographing people in action! It’s the ideal way to hone your camera skills.
If you are already a good photographer, ask your friend who is hosting the party if you can be their ‘official’ photographer. Whilst you shouldn’t expect a fee, it will help you get your name out there and to make people aware of your work. This might help you to get some paid photography work in future, and will add to your portfolio nicely.
If you are just starting out with photography, use a party as a good opportunity to practice. As well as the people you photograph, you will also be able to shoot things like the food and the venue to practice some very different skills.