Experience? Empirical evidence? Advice from others? Online tools? 
White paper? Astrology??
Give me advice, forum. What’s your preferred way to select tire pressure. No method will be criticized (except my own…that’s ok). Just curious to know what everybody is doing.
I used the Silca Pro Pressure Calculator. Because it’s pro. I don’t want to go with some amateur option. 
Narrow it down a bit … for Road, MTB, CX ? All quite different.
Or you mean regardless of discipline? Personally for me - trial and error and chatting to friends (especially for CX where tyre pressures are a never-ending talking point).
IDC. You pick. If the model for Road/MTB/CX is different for you I find that to be very intriguing. Had not considered that might be the case.
Road. Put pressure in. Go for a ride. Think, that felt a bit rough. Next time, put a bit less in. Go ride. Think, uh, that feels a bit sluggish and wobbly. Put more in. Find your happy medium. At the moment, I’m at about 65psi on tubeless 25s.
Cross. Put about 25psi in. Ride round. Let some air out. Ride round some more. Let more air out. Very rarely, put some back in.
Town bike. Uh, that tyre feels pretty flat, have to remember to pump it up some time…
I call that ‘empirical evidence combined with experience’ 
This is a decent starting point.
Usually give the tyres a quick squeeze before a ride. If they feel OK, I’ll head out. If they feel a bit soft I’ll pump them up a bit🤪
I usually ride my 26mm turbo cottons at 7bar, turns out i should be running ~5.5bar according to the silca calculator 
For me it’s just been a combination of (initially) what other riders told me, and since then has been tweaked by experience and preference plus anything I hear on the podcast or read online.
Road - 26mm Turbo Cottons - Currently run them around 95-100psi but as I lose weight i’m continually trying lower and lower pressures. My last set of 23mm GP4000s I used to run at 120psi (what I heard I should do) which was a rough ride for sure and I would not recommend it.
Gravel - 38mm Schwalbe Somethings (look similiar to current G-One Bite) - I tend to run these in the 35-40psi range, lower for more unforgiving surfaces, if I’m riding on paved i’ll go toward the higher side.
Just a full disclosure - I have no idea what i’m doing. Ever.
Silca calc says I should run 85F 87R, currently running 90F 95R and Conti recommends 95 min for the 5000 clinchers. Maybe I’ll lower it a bit and see how that goes.
It should say:
“Ah dinnae ken if it ahll tak onay moar, Captain”
#getScotsright
THANK YOU !!!
(Didn’t have time to find a good one)
For sure start with what @mcneese.chad points out.
Also the podcast marginal gains from Joshua Poertner (owner of Silca) is really good.
For road i use around 70-75 psi, 25mm gp 5000 with latex tubes, for training and racing. I weigh around 69-70kg and the bike around 8kg. My experience, lower is better. Better a bit to low than to high. Although most of my teammates don’t agree…I am right
Scots are unique in the fact that some dialects actually type in their accent. People from Aberdeen-shire (Fit-likers) are most renowned for this!!! 
Enve’s tire pressure chart is quite good. While it is designed to set up Enve wheels, if you know the inner diameter of your own wheels you can use that off their charts.
First I pump them up way too high and then I get beat to death by the road surface. Then I slowly lower by 5 psi every year until I finally started pressuring at a comfortable level.
Probably not the most effective method but that’s what I did haha.
Just in case someone is looking for an alternative to Silca’s online tool. Similar results for me - I like the UI a bit better and it has a couple of more options:
New bike or new tire/rim combo - I start just a hair below the “lawyer label” and move downward until I get a pinch flat if in clincher format. Then consider how low it really was on that day, with temp changes (I used to have a heated garage and would ride in the cold) and compare those conditions to how often I would case the particular crack or rock or whatever.
If the tires were set up tubeless, I used to have a specific cx style course with a couple of really gnarly turns, and I would judge burping based on tire pressure.
I’m a generally heavy person in the cycling world (but not the general American 6’+ world) , and it took me a while to realize that the minimum inflation number printed on the sidewall was absolute dog-dirt. My old LBS shoppies did call me “ham-fist-face,” though.
I like that Sram guide compared to the Silca tool as you know whether the recommendations are for tubes or tubeless. Seems like I need to drop my pressure with my new wider ID rims
I start off by picking the middle of the range stated on the tyre wall. Then, as a general rule, I’ll work backwards towards the pressure that feels comfortable and planted on the road.
Nothing but science there.
