How to chose resettable fuse for 24 V DC to 5V DC converter?
Knowing all this, how do I choose my fuse from all the existing
  models?


Typically fuses are for short circuit currents, and good for removing the circuit from operation if the current goes well above it's intended operation. 

If I were sizing a fuse for a circuit, I usually use at least 50% of the rated current as a starting point, and go to the next size fuse. So in your case I would use a 1A fuse. The fuse size should be high enough to not blow in normal operation (which it will if rated close to the current max).

A better way would be a current monitor with a shutoff if you really must have current protection. A better way is to use a DC to DC circuit that has built in current limits that self limits the current.