If you find yourself preparing to give a speech at a wedding this summer, then keep it brief, is the advice of experts far and wide. Don’t worry if it feels a bit counter-intuitive. Your brevity will be appreciated. “Shortness is sweetness,” says Sarah Kiehl, who heads the Association of German Wedding Planners. “The biggest mistake you can make is to try and include as much input as possible.” She says keep it to five to seven minutes as a rule of thumb. But, her advice is: “Ideally, it should even be just three.” In any case, make sure you practise at home beforehand, so you can speak as fre…