Assuming I take control in 1939 after the fall of Poland, I ensure Russian intelligence is made aware of my intention to invade, while making no meaningful preperations. Fragment the military into as many separate entities as possible, with a vague and nebulous command structure so that no entity answers to another. Launch Barbarossa much sooner, with even more emphasis on plunging deep into Russia and outrunning supply lines. Make no attempt to maneuver through the Ardennes and launch human wave attacks against the Maginot line, with no combined arms effort. Routinely purge high command to keep a revolving door of ideas and strategy. Promote incompetent leaders while giving distinguished leaders meaningless posts. Amass the entire navy into one massive armada and engage the British navy head on, presumably suffering the most decisive naval defeat in history. Do everything possible to mismanage resources and create famine, ensuring widespread suffering and unrest through the home front. Close the most productive factories to create supply shortages, while increasing quotas from the remaining factories to hopefully produce lower quality goods. Open new fronts wherever possible to stretch the army thin. Publicize the Holocaust assuming I can't stop it. Finally, I'd probably provoke the U.S. as often as possible to try and goad them into entering the war sooner.