Put aside the negative for now.
3 can be written 3.000... as many zeroes as you like. Now divide by 4 as if there was no decimal point.
We get 75, but when we write 75 over the top of 3.00 the 7 sits over the 0 next to the decimal point so that's where we put it in the answer: 0.75. Put the zero at the beginning so that we don't accidentally lose the decimal point because of its smallness. The zero protects it.
Now put back the negative: -0.75.