What you really want to do, above the first few thousand feet which should be at full rich, is climb at peak power, circa 100degF rich of peak egt.
A standard Warrior doesn't have an EGT gauge so leaning ROP/LOP is virtually impossible. It also doesn't have a MAP gauge or fuel flow gauge. The only gauge you have related to engine performance is the RPM gauge.
This is from the PA-28-161 Cadet POH:
CLIMB
[No instructions on leaning during climbing in the POH]
CRUISE
Use of the mixture control in cruising flight significantly reduces fuel consumption while reducing while reducing lead deposits when alternate fuels are used. The mixture should be full rich when operating above 75% power, and leaned during cruising operation when 75% power or less is being used.
To lean the mixture for best power cruise performance place the mixture control full forward and set the throttle approximately 35 rpm below the desired cruise power setting, and lean the mixture to peak rpm. Adjust the throttle, if necessary, for final rpm setting.
[...]
Above 6000 feet, the engine is incapable of producing more than 75% power.
[...]
DESCENT
Normal Descent
To achieve the performance on Figure 5-31, a power on descent must be used. The throttle should be set for 2500, mixture full rich and maintain an airspeed of 126 KIAS. If carburetor ice is encountered apply full carburetor heat.
This suggests that during the climb you should be running full rich all the time. However, if you look at the performance charts for a climb, then you'll find that the numbers in it are based on "lean mixture per Lycoming instructions". But these instructions are not included in the POH... In fact, later on (in the Airplane Description) another reference is made to the Lycoming Operating Manual.
Personally what I would do in a Warrior (no EGT) is simply lean for maximum RPM, once above 6000 feet, to obtain best climb performance.
Oh, and if you look at the performance chart for the descent you'll find that if you follow the instructions, the descent from 10.000' takes about 12 minutes, or a little over 850 fpm. This might be a bit uncomfortable. As someone else suggested, you'd better aim for about 500 fpm, particularly if you have passengers.