Totally depends on the mountain, for one thing.
Some have trees. Some have rocks. Some have dirt.
Can I drive close enough to carry stuff in several trips?
Do I have to haul a 60 pound pack for 2 days to get there?
It also depends on what sort of operation you are planning.
My standard antenna is a
dipole kit, with separate wires
for each band that I can use in any combination. Usually
I hang this from a tree, but I’ve tied it between rocks,
propped it up on my hiking staff, or otherwise improvised
when needed.
These days there are many options for telescoping
fishing rods if you need to carry your own support, or I
have some sectional tent poles that I can use.
The simple option for operating is to sit on the ground
with the rig in my lap if there isn’t a convenient rock.
Sometimes I’ve wished I had a small foam pad, and
sitting on an ant nest is not recommended. You
certainly can haul in a folding camp chair and table
if your weight budget permits.
VHF FM is easy with an HT, at least for casual contacts.
A small yagi can be held by hand, at least for a short
while. More serious operation may call for a longer
beam on a mast, both of which can be lightweight and
collapsible.
Probably the most important thing to remember is that
there is no “one right way” to do it. See what works
best for your own personal operating style, preferences,
comfort, and adapt as needed for your specific location.
If you can’t drive stakes for guy ropes, you may have to
use fabrics shopping bags full of rocks for anchors. In
other cases, you might secure it to a signpost with a
bungee cord.
A good starting point might be to try setting up in your
driveway, patio, or a parking lot, to see what works for
you and what doesn’t. At least it is a shorter walk to go
get more rope or a clipboard to write on when you find
you need it.