√ Rosh Chodesh -the beginning of the Hebrew month- is a semi festive day. The hierarchal order of the Jewish festive days is: Shabbat, Yom Tob, Chol haMo'aed, and then Rosh Chodesh. In the times of the Bet haMiqdash, when there was a special qorban (sacrifice) offered in Rosh Chodesh with sounds of Shofar and trumpets, men used to avoid working in Rosh Chodesh. Today, in some communities, mostly Ashkenazi communities, women do not work or refrain from doing certain melakhot during Rosh Chodesh.
√ In Rosh Chodesh we are indicated to behave and be in a happier mood (ra-ui lismoach bahem). As we said, although it is not forbidden to work on Rosh Chodesh, it is meritorious to celebrate Rosh Chodesh with a special meal (Shulchan Arukh, OH. 419:1). This is done by having some foods on Rosh Chodesh which are considered luxuries foods, particularly meat and wine (By the way, this is the reason why Sephardic communities refrain from eating meat during the month of Ab, only from the second day of Ab, once Rosh Chodesh is over).
√ It is forbidden to fast on Rosh Chodesh. It is also customary to avoid visiting the cemetery on Rosh Chodesh. Most cemeteries are closed for visits on Rosh Chodesh. When the anniversary of a loved one (sal, yohrtzait) falls on Rosh Chodesh it is customary to fast or visit the cemetery before or after Rosh Chodesh. For this same reason -some exceptional cases apart- eulogies should not be delivered on Rosh Chodesh. Depending on the circumstances, rabbis will rather deliver a Debar Tora -general words of Tora wisdom- in honor of the deceased, minimizing personal emotional remarks, which might cause an additional sadness to the audience.
Rosh Chodesh Mar Cheshvan is celebrated today and tomorrow.