1) The Gemara (Taanis 29a-b) tells us “Mishenichnas Adar Marbim B’Simcha- when the month of Adar arrives we increase our joy” as it says in Megilas Esther (9:22) “V’HaChodesh Asher NehePach M’Yagon L’Simcha…The month (Adar) that was turned from sadness to happiness”
If one has a courtcase with a non Jew, it is good to schedule it for the month of Adar.
2) Our holy sages, the Chazal instituted the reading of 4 special “parshiyos” in (or near) the month of Adar, as a commemoration of 4 special Mitzvos (which we will elaborate on a bit in the next few days)
The first of the “4 Parshiyos” is Parshas Shekalim (which we will iy”H be reading this coming Shabbos, and can be found in the beginning of Parshas Ki Sisa Perek 30 Pesukim 11 thru 16). This reading is to commemorate the Mitzvah of “Machtzis Hashekel”, the half Shekel coin which every Jew was obligated to give each year to the special fund from which the daily Korban Tomid (sacrificial lambs that were offered in the Bais HaMikdash each morning and evening) was purchased.
Although we do not have a Bais HaMikdash today (an unfortunate fact which will change very shortly iy”H with the arrival of Mashiach), we “perform” this Mitzvah by reading about it in the Torah.
There are some opinions that this reading is a biblical obligation (Elya Rabba Siman 685 in the name of the Rashba to Brachos 13a who maintains that all 4 Parshiyos are biblical obligations). However, most Poskim maintain that it is a rabbinic obligation.