How important is it to write a business plan BEFORE you start your business?
I'm thinking of starting my own fabrication business, but am wondering whether I should write a business plan straight away or see whether I can get some customers first?
It depends on how much you intend to invest in it, also time-wise.
If it's just a couple hundred dollars that you dont mind losing you can do what you want. But if you have to set uo a business, get a loan and and so on you should consider and overthink the situation carefully. So there are no surprising that you havent considered. It's mostly a tool to aid you, but also a means to sell your business to others.