Some

But what if I want to use the LED I linked earlier? (http://no.farnell.com/kingbright/kp-1608surck/led-0603-230mcd-red/dp/2290329) Which resistorsizes should I go for?

Your question is like asking, if I have a stake, how long should I cook it? We have no idea how warm/cold it is when you put it on the grill, temperature of the grill, distance from the heat or your definition of medium rare.

For $12 you can get a big pack of resistors of 68 different values and then diddle with it until you are satisfied.

 

But what if I want to use the LED I linked earlier? (http://no.farnell.com/kingbright/kp-1608surck/led-0603-230mcd-red/dp/2290329) Which resistorsizes should I go for?

I have given you two different versions, one which drives the LED with 500uA (which may be too dim in direct sunlight), the other with 8mA (which will likely burn your retina if you get too close). Try both and see what you like.

 

But what if I want to use the LED I linked earlier? (http://no.farnell.com/kingbright/kp-1608surck/led-0603-230mcd-red/dp/2290329) Which resistorsizes should I go for?

Calculate the LED current limiting resistor in the normal way - and double check it doesn't exceed the capability of the open collector output.

If the LED is sensitive enough for a residual glow, calculate a shunt resistor to load the maximum anticipated leakage current to less than the LED Vf.

Maybe dimension the shunt resistor for about 3 - 5x the leakage current.