Whether it's something as straightforward as the season, a theme gives your wedding a cohesive look while limiting your choices—both of which can end up saving you money, says N.Y.C. planner Marcy Blum. A theme also provides a springboard for finding alternatives to expensive big-day items. For example, a full bar can tack zeros onto your total bill. Instead, try serving only a few cocktails, along with wine and soft drinks. For a wedding with a vintage feel, old-fashioned but hip rum drinks, such as mojitos and Havana coolers, provide a sophisticated twist on the signature cocktail.