1st: using the right proportion of meat (with the right level of fat) and onions and make them mix all well together so kabab does not fall from the metal skewer on the BBQ.
A trick that you could use here ( to make sure they won't fall on the BBQ): use a thin string and wrap the meat with it loosely ( the turns should not be very close together) and when it is cooked separate the strings from the meat by just unrolling it.
A quick note on how to make saffron: add about 1/2 teaspoon saffron to a cup ( in powder, I buy them in strings, in original form, then powder them myself),add small amount of boiling water and mix it well,so the water becomes a very intense orange color. to get even more intense, you could put the small cup inside your rice pan while you cooking your rice and steam it. then you can mix it with your rice.