Before there was a standardized calendar, and after the date of Rosh Chodesh could no longer be communicated by fires, when the sanctification of the new moon had to be transmitted over distances, was there any particular practice or observance of Rosh Chodesh other than the korbanot in Yerushalayim?
Since there were still sacrifices, I don't know if there was a musaf davening to add. I don't know if people said hallel on holidays or if there was any formal bentching into which someone could insert ya'aleh v'yavo.
As far as I can figure the minhag for women of not doing certain melachot must have developed later as, unless every Rosh Chodesh was marked on two days outside of Israel, people would not know what day was Rosh Chodesh. Yom Kippur Katan must have been a later development as well unless it was held for two days because without the say-so of the Sanhedrin, how could someone know definitively when the next day was to be Rosh Chodesh?