Responding to a Twitter chat we were discussing the splitting the middle term method (which some students have difficulty with); if one must have a recipe to follow – try the box method. I always encourage students to check coefficients first, if the coefficients of x2 and the constant are prime they clearly do not need elaborate methods.
Working on Quadratic Grids from Underground Mathematics will help students develop and understand the method.
For instructions on the method:
Quadratic Factorisation Box method (pdf file)
An introductory post on Underground Mathematics is here and you can view all posts in the category Underground Mathematics.