Often your caterer will cut and serve a tiered cake as part of their service, but you should ask your caterer.  I also offer a cut/serve service that includes cutting the tiered or sheet cakes, serving, boxing up any left over cake, and tidying the cake table.  You will need to provide cake server/knife, plates, forks, napkins, toasting glasses, and cake topper if you use one.  I offer cake stand and display rentals and work with wedding stylists and rental companies to assure your dessert table is picture perfect!