The performance section of your RFM should be able to tell you whether you have hover OGE capability at the relevant weight, altitude and temperature.
As a rule of thumb, give yourself a 10% thrust margin for confined area - ie make sure your AUM is 10% less than the max for the altitude and temp for hover OGE.
Obviously, include this in your planning before takeoff, 'cos you dont want to be looking through the graphs in flight!
Do the manufacturers recommended engine power checks before take off, or check that you can pull to your aircrafts max continuous torque and takeoff power settings without topping out on Ng or temp (if we are talking turbines) or whatever other limitations you have in piston engines (manifold pressure?/temp?) at the altitude of the LS on the day.