Chazal tell us “Mishnichnas Adar Marbim BeSimcha” (Adar brings with it happiness).  Thus, if one has a court case with a non-Jew one should try to have it during this month.

MeSheNichNas Adar Marbim BeSimcha really refers to removing sadness and worry but not necessarily including activities of simcha.

Many hold that MeSheNichNas Adar Marbim BeSimcha applies to purim katan in the first Adar during a leap year.

Beginning Rosh Chodesh Adar, some have the custom to hang a sign which says "Mishnichnas Adar Marbim Brsimcha." Some have the custom to place this sign covering the "Zecher Lechurban" unfinished part of a wall that is usually left in the home.