Studying Tehillim on Rosh Chodesh:
It is an ancient custom, on each Rosh Chodesh, to study one verse of the chapter of Tehillim that corresponds with the current years of a person’s life. The verse should be studied with the commentary of Rashi, and additional commentaries may be added as well. If the current chapter contains less than twelve verses, or in a leap year, when there are more than twelve months, verses that have been studied on a previous Rosh Chodesh should be studied a second time. Similarly, if the current chapter contains many verses, then two or three verses should be studied at once on each Rosh Chodesh of the year.
“Every Rosh Chodesh the spark of Moshiach, also known as the ‘Yechida’, which is in every Jew’s soul (which is a spark of the general Yechida – the soul of Moshiach) is revealed.
The revelation of this spark resonates and causes a rejuvenation in the entire being of every Jew, so that everything he does in permeated with the level of his Yechida,
And, most importantly, through this the revelation and arrival of Moshiach is caused in the most literal sense – “a king from the house of David”, soul in body etc.,”
– Sicha of Parshas Toldos 5752