You'll want to bring any photos you've pulled that represent your style and ideas. Will you have a wedding cake and groom's cake or are you more interested in cupcakes or some other pastry? Do you have any food allergies or strong flavor preferences or dislikes? There is no point in trying a lemon something or other if you absolutely can’t stand citrus, etc. But also consider your guests and the flavors that will appeal to a majority of them.
Each bakery will put their own twist on tastings, but basically, you will have the opportunity to sample a variety of flavors paired with various fillings and/or frostings. Be sure to cleanse your palate between bites of different flavors. Your bakery consultant will direct you. As long as you’re tasting with an experienced, reputable bakery, trust that they know what they are doing and rely on their guidance regarding flavor combinations, design and amount of cake. Most of all, have fun with it!