Engagement Party Etiquette.

flower_blkTraditionally, the bride’s parents host the first engagement party traditionally. However, if the bride’s family was not able to do it, the duties would fall to the groom’s parents. Today, those rules don’t really apply, as any friend of the couple can offer to host the event, especially if the couple’s family lives far away. Just make sure you’re not stepping on any toes by playing host.

As for tips on a more formal etiquette, Martha Stewart is  a good place look.