No secrets. Platinum Premier is normally awarded when you've reached over 125 nights for three years in a row. (at least that was the requirement when I made it some years back). While the literature is silent on the actual stay requirement, seems to be a function of looking at the tops two to three percent of Marriott Rewards members in terms of annual stays. PP confers a separate number to call, a set of folks who are part of the Platinum team at Marriott Rewards, and a more welcoming feel when you call in. The card you get read Platinum Premier and is good for one year. In past years the annual renewal required a 100 nights stayed. Not sure if that's still the case, though. If you don't make PP, remember that every night beyond 75 is a roll-over night and then added to your total for the coming year. Hope that answers you question.
There is a level that is not necessarily "secret" but is unpublished, Platinum Premier. There are no published standards that gauge entry to that level, however it is rumored to be the top 3% of all MR members. Most members that have achieved it (myself included) generally stay 140nights or more a year and have done so for more than 3yrs. That alone does not entitle you to the level, as there are rumored to be other factors that play into the decision. If you search the forums you can find many discussions related to this from other members with other thoughts of how you attain Premier.