Question

While splitting the middle term do we have to write the biggere or smaller number first

Answer 1

Its completely your choice. Just write the stuff that's divisible by a common number together. :) 
e.g.  3 x^2 - 4x + 1 
     =  3x^2 - 3x - x + 1
Keep the 3's together as they are both divisible by a common number. It'll be easier :)