Does anyone have personal/practical suggestions of how to increase one's simcha in Adar?
The short answer: Get ready for Purim, by learning about why Purim is a joyous day and start internalizing those happy lessons.
I already wrote here, about 2 reasons why we increase joy in Adar - as a preparation for Purim. To recap:
Practically speaking, you could start by studying the above 2 passages, to gain a better understanding of the reason behind the joy of Purim and how to prepare for it.
You could then learn relevant Midrashim on the Megilla related to the ונהפוך הוא and the קבלת התורה .