The standard advice has been to take 1 adult aspirin about 20 minutes before the dose. This works reasonably well for most people. Another approach I recently heard from a patient was to take 3/4 cup of applesauce directly before taking the dose (in this case it was 2000 mg a day). The patient reports she has had no trouble since.
Comment: This is a new one for me. It sounds like a great idea. I certainly prefer applesauce to an aspirin. For any of you in the community on niacin, give this a try and let me know how it works for you. Our own little Portola research project!