The Moon (Tai Yin, 太阴) in the Self palace (Ming Gong, 命宫)

What the classic says, Zi Wei Dou Shu Quan Shu (紫微斗数全书), volume two

The essence of water: a round face, a mild temper, clear-featured and clever, drawn to wine, writing and study, and able to make a name sideways. At Rooster (酉), Dog (戌) or Pig (亥) it has its ground and the name carries. Well placed with the Power transformation (化权), clear-minded and honoured — mild, respectful, thrifty, and clean in office. Badly placed among harsh stars, with the Millstone (陀罗) and the Flare (火星) met, hard straits.

太阴水，南北斗化富，为母宿，又为妻星，为田宅主。太阴居命面方圆，心性温和，清秀耿直聪明，花酒文章，博学横立功名。太阴入男命吉凶诀：太阴原是水之精，身命逢之福自生，酉戌亥垣为得地，光辉扬显姓名亨。太阴入庙化权星，清秀聪明贵无伦，禀性温良恭俭让，为官清显列朝纲。太阴陷地恶星中，陀火相逢定困穷，此命只宜僧与道，空门出入得从容。太阴入限吉凶诀：太阴星曜限中逢，财禄丰盈百事通，嫁娶迎亲添嗣续，常人得此旺门风。

The classic also has lines on a woman’s chart, reading a life by its sex; they are left out here, in the Chinese as well as the English. The source link has the full text.

“Well placed” and “badly placed” refer to the star’s brightness in the branch the palace falls on: the same star in the same palace reads differently bright and dim, and the clause says how.

Source

And in the chapter of questions on the stars (Zhu Xing Wen Da Lun, 諸星問答論)

well placed and with benefics gathered, wealth and standing

在身命廟樂，吉集主富貴

How this placement actually turns up

• Well placed (exalted or strong) in 51% of those charts, badly placed (fallen) in 23%, in between the rest.
• Alone in the palace in 49%; sharing it with The Sun (太阳) 17%, The Strategist (天机) 17%, The Blessing (天同) 16%.
• Carries a birth-year transformation in 53%: Fortune (化禄) 11%, Power (化权) 11%, Merit (化科) 21%, Trouble (化忌) 10%.
• How often the conditions the classic’s line names actually occur — one of the four difficult stars (擎羊陀罗火星铃星) in the palace with it: 30%; Earth Void or Earth Robbery (地空地劫) with it: 15%; Lu Cun (禄存) with it: 8%.

Counted by casting every day from 1950 to 2009 at each of the twelve hours — 262,980 charts, 8.3% of which have The Moon here (every main star sits in every palace in about one chart in twelve). A count, not a reading.