Once you hit your mid-20s, it may feel like you have to go to a different wedding every weekend. But there seems to be a lot of ambiguity around wedding etiquette. Times have changed since the days of ultra-formal nuptials, but what about the "rules" for today's guests? Do you really have a year to give a gift? Is it ever okay to ask for a plus-one? Sometimes it's hard to know what to do (and what not to do).Weddings may be more hip and modern since your parents got hitched, but it turns out some etiquette rules never go out of style. We asked Lizzie Post, great-great granddaughter of Emily Post and co-author of Emily Post’s Wedding Etiquette (sixth edition), and Jennifer Spector, newlywed-at-large for online wedding registry site Zola , to help us navigate the tough questions. Ahead, we've compiled their advice into 10 essential rules every twentysomething should know in order to be a gracious wedding guest.