Each wedding cake-maker has their own style and area of expertise; this is a highly specialised skill and standards can vary enormously. Personal recommendations are usually a good idea. A cake at someone else's wedding may have impressed the couple.
The bride and groom should go for a tasting and discuss their wishes. They can look through an album of what other couples have chosen, and choose a cake from a portfolio. They may wish to order a cake made to their particular requirements and sketched by the cake-maker.
Make sure that the cake-maker is well briefed on where the cake is to be delivered on the day, the timings and the positioning of the cake at the reception.