I suggest try getting into your customers' shoes. What do you want the most? Try to answer that question with your slogan, domain, name etc. That is challenge #1 (the biggest challenge). Then challenge #2 is to find a clever CONCISE way to express it. Try brainstorming. Don't worry if the first ones are long and clunky, they will eventually lead you to short and clever!
Unlike you, this is my favorite part of business! I'll trade that task for the drudgery of record keeping and all the other non-creative jobs ANYDAY!! 
