How to reversing stem rotation for Pfister 910-030 cartridge

Leaking from the stem or handle 90% of the time means all you need is a new cartridge or new O rings or seals, depending on the model of your faucet.
Phister has a warranty https://www.pfisterfaucets.com/parts-support/warranty-information
and if they are like other faucet manufacturers with a similar warranty, just take the bad part(s) to your local authorized Pfister dealer and they will exchange them over the counter. Otherwise, you can contact Pfister through their website.

If I am not mistaken, the stems are specific to hot or cold. They turn in opposite directions. Someone may have put a hot stem instead of cold when doing a prior repair.

You may need to replace the cartridge(s) or rubber washers on the valve stems. Depends on what model faucet you have.

flip the locking ring at the top of the stem

On this valve the hot/cold in reverse is easy enough to fix, but the faucet dripping at the handle is another issue. To reverse the hot and cold, turn off the house water, relieve the pressure by opening a nearby faucet. Once the water stops, remove the handle and faucet cover so you can see the valve. then the four screws that are visible need to be removed. Mark one of the screw holes with a crayon or pencil and then remove by pulling straight out. Once out, inspect the main o-ring right behind where it sits against the valve, (if this is damaged, it might be why the handle area is leaking) then turn the whole assembly clockwise 180 degrees then insert straight back in and insert screws. Tighten screws until snug. Turn water back on before installing cover and handle to check for leaks. If no leaks are found, install cover and handle and check for proper position of hot and cold. If there are leaks, tighten screws in clockwise rotation tightening each screw a quarter turn, then moving to the next one until dripping stops. If dripping is from center of stem, where the handle attaches, you will need to contact Price Pfister to request a replacement. They are very good to work with. Good luck.

Replace the stem assembly (ceramic cartridge) with Price Pfister service part #910-030. Be sure to turn water on briefly to flush out any debris in the valve body before installing new part. NOTE: this valve does not like old galvanized plumbing.

After you remove the chrome collar and plastic collar washer (behind the faucet handle), pry the beauty plate off the wall. Turn off the house main water supply. Remove the four screws and washer holding the cartridge and valve stem in place. Save the metal washer under the four screws for use with the new cartridge. Replace the stem/cartridge assembly and secure with the saved metal washer and four screws. Reinstall beauty plate, collar & collar washer, then handle.

There could be debris wedge in the cartridge of the faucet. If you have tried pulling the cartridge out to see, and you are still having these issues, more than likely it is a defective cartridge; in which case it should still be under warranty. If you haven't tried this, then I would recommend doing so. Just be sure to turn water off to your faucet first.

There is no seat replace cartridge/stem

sounds like you have a single lever shower, in this case the valve stem which mixes the hot and cold has a clogged hot side , you'll need to remove and replace the cartridge or valve stem