Tianmenshan is fairly straightfoward in comparison to Zhangjiajie. The main thing that's confusing is the plethora of different transportation methods. When you're buying your ticket, you have to pick a route, which will dictate which ones you take in which order. There isn't a hiking route, so you'll have to use some combination of these.

To help lay things out, first I'll define some locations.

• Upper Ring
  • this is the two walking paths (east and west) on the top of Tianmenshan, which form a ring around the mountain.
• Tianmen Cave
  • this is the "hole" in the mountain for which the mountain is named.
• Mountain Plaza
  • this is a plaza from which the stairs to Tianmen Cave starts
• Mid-mountain Cablecar Station
  • this is a cablecar station that is NOT the one you start from. It is at the foot of the moutain.
• City Cablecar Station
  • this is the cablecar station that all tourists start from.

Now for the transportation options. All of these are two-way (although, you can only go one way for each route)

• Cableway (also sometimes called "large cableway")
  • This goes from the City Cablecar Station to the Upper Ring.
• Escalator
  • This goes from the Upper Ring to Tianmen Cave
• Tianmen Stairs
  • This goes from Tianmen Cave to the Mountain Plaza
• Tianmen Cave Escalator
  • This is an optional escalator that goes from Tianmen Cave to the Mountain Plaza
• Expressway
  • This is ALSO a cablecar that goes from the Mountain Plaza to Mid-mountain Cablecar Station
• Cablecar Shuttle Bus
  • This is a shuttle bus that goes from the Mid-mountain Cablecar Station to the City Cablecar Station

So, as an example, A route, which is what I ended up taking, starts from the City Cablecar Station. It then goes:

City Cablecar Station -> (Cableway) -> Upper Ring -> (Escalator) -> Tianmen Cave -> (Tianmen Stairs) -> Tianmen Plaza -> (Expressway) -> Mid-mountain Cablecar Station -> (Cablecar Shuttle Bus) -> City Cablecar Station

A note on availability and the VIP package

If you're booking late, some of the routes may be sold out, especially for the timeslots you want. A way to pay-to-win out of this, if you want to go on route A (which is the most popular, I think?), on trip.com and probably other sites, you can pay ~20 more for the "VIP" package.

What this means is that instead of going into the turnstiles, you go into the "VIP" "lounge" (note: the office only opens after 8:00am). After doing some processing, you'll go to the third floor, right where the cablecar is, and the worker there will acknowledge the bribe you paid them and let you on immediately.

It's almost never sold out, since $20 (it's almost twice the price of the normal tickets) is quite a lot in local currency, but if you're a foreign traveler making plans on the fly, it's worth considering.

Weather

Weather is what it is. Apparently it rains 200/365 days, so there's a 66% chance it's raining or cloudy. For what it's worth I think the cave itself can be quite spectacular in the clouds, although the views surrounding it suffer somewhat. If the clouds are covering the "gate" from the bottom, it may be worth it to wait a bit of time to see if it clears up.

Hotel Change?

I see a lot of articles recommend changing your hotel from Wulingyuan to Zhangjiajie, but personally I find it a huge hassle to change hotels. It's a ~30 minute DiDi from Wulingyuan to Zhangjiajie, and it cost 50-70 RMB, which is like $10 one way. Personally I just DiDi'd there and back and it was fine.