A successful event relies on a combination of empathy with your attendees along with fulfilling your client's objectives. I also believe that if people have given up their valuable time to attend your event that it's your responsibility a) to make an impact b) make it something they'll never forget c) to get them pissed, or d) all of the above.
The impact might come from sending out a gang of Harley Davidsons to deliver the potential client management team to a remote pitch location. Or hiring a church and employing an actor to be a fervent preacher delivering a pitch in the form of a sermon. Perhaps flying forty six journalists to Iceland to sample camera quality by taking pictures of a catwalk show staged on top of a glacier. All of which I've had great fun doing.
I've learned two crucial lessons from my time organising events. The first is to pay painstaking attention to every detail - no matter how minor they may seem. The second is to never, ever underestimate the Power of the Goody Bag.