How can I train myself to "think outside the box"?

Question anything, Even your best Ideas, Even yourself

A simpliest way, that you should listen to everyone but follow no one, then you could get a real chance to do something and think beyond, like your question"Outside the Box" :)

That's a century old question. We have moved on.

In the age of millennials; the accountants have taken over. It is not so much about being "out of the box" as much as "understanding the box" and delivering the most efficient relevant message that triggers sales. So if you have a fantastic out of the box communication and a "regular" communication that delivers numbers, the "regular" communication wins hands on every time.  

Just like most movie director cuts, they never make it to the big screen.

Focus on what you're trying to achieve, understand your objective fully and you'll start to find the solution unfolding (that usually works for me!)

By continuously challenging yourself and evaluate the situation as if you are an entrepreneur and can play a pivotal role in changing the dynamics  in your favor.

Positively listing and getting 360 degree feedback is the most important  aspect in order to think out of box and taking right decisions and right time.

Always challenge yourself that you can do the impossible. Don't settle for something simple, re-create you're ideas to be more creative.

determination of position as freelancer with diagnosis of the current situation or dilemma , as well as possible future effects consider the geopolitical parameters and macro economic metadata , as well , all possible methods for avoid such plight and gain tasks 

To believe in yourself  and by breaking "walls " built in the head and allow free flow of thoughts

Take a situation and ask others for their opinion how they will respond or react to that situation and understand how they think. Now you need to practise how to think in a different way to handle the situation effectively than the others. So start practising this in every situation you come across and this method will help you to improve your thought process. May be you will make mistakes initially but your sincere effort will help you to achieve your goal. Good Luck.

Read a lot, think deeply, question yourself while thinking, right down the ideas that you have got.

Don't put yourself in a box. Thereby negating the need to think outside of it. Boxes and restrictive thinking are false preconceptions thought to use by an educational system bent on teaching through repetition and learning things that have been decided upon by individuals that have preceded us.