no, its not always the largest or smallest first.

you want to plug in in such a way that the first two terms and the last two terms factor so that you can get a common factor among them. in this case it doesn't matter:

let's say you use

2x^2+16x-3x-24

= 2x(x + 8) -3(x + 8)

= (x + 8)(2x - 3)

if you used

2x^2-3x+16x-24

= x(2x - 3) + 8(2x - 3)

= (2x - 3)(x + 8)...............same thing