Agree with others that the easiest method is to find a route (or two) you’d enjoy traveling, and buy an F/D1 ticket to gain MQDs. Basically just spend money.

Another option is to burn a Choice Benefit on an MQD Accelerator (1000 MQDs for PM, 2000 MQDs for DM). Note this is only worthwhile if you see where the Accelerator will actually push you to the next tier when factoring in pending MQDs and travel you feel sure of accomplishing.

My husband (DM this year) was rather disappointed he would likely fall to GM next year, but after running the numbers carefully, the Accelerator mentioned above, combined with a paid F ticket for travel that just popped up in a few weeks, he will squeak out PM for next year, which to him is valuable as he normally books Y and enjoys the auto UG to C+.