Probably sitting but whatever works better for you I guess. I tried both ways but find sitting is easier as I can make micro corrections easier than standing.
So basically what your saying is its a preference. There is no right or wrong way?
Be able to do both. I can still stand the longest sitting down though.
Do it both ways. Sitting down is good when you’re on a rolling trials line, and standing up is good when you’re on a hopping trials line.
yeah, I like to still stand standing, i can hold it a little longer i think, but for riding skinnies i do sitting.
Well if you are practicing still stands to be able to ride skinnies, then you might want to sit down because it is harder to ride in a straight line while standing up.
EDIT: unibikeling and phlegm beat me =)
Well, whichever way works best for you would be the right way for you. Try both ways for a while and see which works better for you. It might be advantagious to learn both ways.
If your seat post is really low for a particular type of riding, it might be harder to still stand while sitting since your knees will be really bent, and if the saddle is really high, you might not be able to have much clearance when standing on the pedals, in which case, sif still standing! 
While we’re on this subject, I’d like to hear from the really good still standers as to what psi do you prefer, and can the tire type/size/width/sqarer/rounder make a big difference in making it easy or more difficult.
Probably hit the “sumbit” button once…it didn’t load right away, so he clicked it again, and inadvertantly posted twice. That’s happened to me a few times.:o Maybe by the time he realized it, the edit time had expired.
Btw, who else thinks the edit time is waaaay too short, and maybe should have no time limit? Many websites use this same template with the same options, but most have no edit time limit at all.
while here, I’m going to post some of the things I found helpful while learning to still stand.
Today I found it helpful if I pushed down a bit on the pedal to get up instead of just jumping on the unicycle.
Sitting down. Plus, all the people I’ve noticed doing really long stillstands, like a minute or more, seem to be sitting. For me I find it allows me to relax more, and I seem to be able to balance longer when I’m relaxed. Same worked for me last week at NAUCC in the Slow Race! The hard part is relaxing when the clock’s running and “it counts.”
Stillstand contest at Unicon 12 (something like 15 minutes)
Video of another contest, at the track, 2 minutes in. Note what appear to be relatively relaxed lower bodies, with all the movement upstairs.
Since the purpose of a stillstand is to stand still and not go anywhere, I’m not assuming riding skinnies or other stuff. But if your seat height is really low, sitting might not work as well as with a taller uni.
Unlike what others are saying if your seat is really low it is a bad idea to stand while still standing. Ive found that if I put my seat really low and stand up, when I’m correcting my balance and moving my body the seat can flop around, and even fall out from behind you. This is especially dangerous when riding rails later down the road.
Learn both ways, but make sure your seat wont flop around too much if you stand up.
I sit down for still lands, but besides that point which everyone else has mentioned. I find you have more control by getting your feet on the very outside of the pedal, like a wide stance.
Stillstands are one of my best skills, and I got good at them by doing them whenever I’m tired of unicycling or I’m just talking to some one. I think it just comes natural if you just practice over and over again. There really is no technique.
I have experienced this myself. Had an interesting fall off a bench.
Listen to this man’s words, for they shall save your from pain!
Do not listen and seat drag that rail!
I’ve noticed a big problem is that I can do a long still stand if I mount hold onto a pole, then let go. But when I have to still stand straight from a mount, I’m horrible, ANy Tips?
Practice.
Would that not wear out extremely quickly doing seat drags?
Would that not look extremely awesome doing seat drags?