if you are going to use water, I would do the following:
1) start with at least warm water, if not semi hot to hot. Why use all the fuel and time to just heat the water
2) Fill it up or at least 2/3rd I would say. I would think what you don't want to do is stabalize the temp and then the water evaporates away and you then have a jump in temp
3) Per Neil comment above, many don't use water. I am still a bit of a rookie and for now I am not there yet, but may try going waterless (maybe with a terra cotta saucer or something) soon.