To get the children thinking mathematically first thing on a morning, I write a number on the board. It can be any number depending on the children's abilities.

Then I ask them to tell me about the number e.g. if the number was 12, they could tell me that 6x2=12 or it has 1 ten and 2 units etc...

Continue until they have run out of ideas. This is an excellent starter or filler.