I spend about 3 weekends a month in Mammoth. I spend most of my time skiing 23 and the upper gondola. I ski lots of Dave's, Hangman's, Climax and the Paranoids. On a typical lap I might take the gondi up, ski Hangman's to 23, then take 23 to the Paranoids which takes you back to the lower gondola. I also ski the dropout chutes a lot, dropout 1 has been skiing well this year. Hangman's is pretty bad right now, but there might be a couple of storms by the time you get here. From the Paranoids you can access Philippe's, which is really fun, but I have not yet been there this year due to low snow, I don't even know how skiable it is. This has not been a good year, but because we got a good base early I have gotten good turns. I would say dropout 1 and the Paranoids are skiing the best right now, with Dave's also quite good. Climax is still a bit bony, but there are some good turns to be had. With Climax I usually either ski skier's right, which is under a cliff area and stays smooth, or far skier's left. The far skier's left is called Sign Line, just don't go past the closed signs, you will be above a huge cliff and patrol won't be happy, I've seen people have to get roped out of that area before because they got stuck above the huge cliff. Incidentally, Sage Cattabriga-Alosa hucked that cliff during a big snow year during Super Park about 15 years ago. He did get busted and fined, but the patrol gave him props. The mountain is really fun right now, despite a mediocre snow year. Dropout 1 has a couple of little rocks to hit too. The chair 5 area can also get good windbuff, and it has some fun little rocks to drop.
There are some pretty crazy lines off the top of Mammoth, stuff in the Top of the World and Kiwi Flat, but it is a low snow year so that stuff is not really a go right now. Things could certainly change by the time you go though.
On weekends the upper gondola can have a bit of a line, if I'm not getting enough laps I head to chair 23, which accesses the top, and chair 22 which accesses Lincoln Mountain. Chair 22 is really fun, good trees and the avy chutes, which are great. 22 is almost never crowded, and it has some of the best terrain on the mountain, so if it is the weekend and you are not getting enough laps on the gondi you might try to go to 22.
On storm days the top of the mountain is rarely open, I ski chairs 22 and 25 then. They access the same peak, although chair 25 does not go as high. 22 has better terrain, but 25 gets tracked out more slowly so I usually go there.
Mammoth also has a sick park, although I don't go there much. Actually, they have like 3 parks.
I don't party much when I'm up there, but I sometimes go to Lakanuki in the village for happy hour. Their specials are good. Roberto's has great Mexican food. Loco Frijoles is definitely a must for Mexican, great food and big portions. Very authentic. Where are you staying? The trolley will give you access to the village from lots of places so you won't have to drink and drive. Also, the mountain has limited parking, so on weekends I use the bus to get to the mountain. They run every 20 minutes and it makes things much easier.
Here is a bus map and schedule. I very rarely drive in Mammoth.
Mammoth is one of the best mountains in North America. It is underrated because it is tough to access for people not from southern California. Have fun, because the wind keeps things smooth conditions are usually good. Even in a low snow year, like this one, there is some great stuff to ski.