If your a newer member, say joined in February, and can extrapolate out what a 12 month stay pattern would look like, call the Rewards Elite Desk. They may look at your history and see that your normal stay pattern would equal Platinum. There are threads on here that people have attained an Elite level by taking a less than 12 month challenge.
If you're a long term member and just trying to add enough nights to hit Platinum...
1) The Caribbean hotels are offering a free night with a stay. Not sure the details, but if you were heading there, check it out.
2) Try to include an overnight for your Holiday shopping excursions. Most areas offer a MEB code that has very attractive weekend rates. Maybe treat the family to a getaway at the reduced rate and rack up a few nights.