Many people ask what advice do I wish I'd been given before I started OpenLX and while transient flashbacks of working well past midnight elicit an overwhelming urge to respond “Don't do it!” overall starting a business is amazingly rewarding. Joking aside, there are always things that you wish you'd known earlier, done earlier...or avoided altogether.
Probably the best piece of advice that I can pass on, though, is: Focus on what you're good at. This is why you started the business in the first place; because you're good at copywriting, because you're creative, because you can design new products, etc. Try not to waste too much of your time on the day-to-day running of the business (once you've got things up and running); your time is more valuable elsewhere. Get something in place to deal with it.
So work out what value your skills bring to the business and consider outsourcing anything that you can pay someone else to do for less. You are what makes your start-up unique; you need to exploit that power and skill-set as much as possible to make your business a success.
One of my other favourite tips – and one that it's always useful to remind yourself of, however long you've been in business – is: Never think that you know it all. Even when you've been running a business for years, there are always new things to learn (and old things to remember!).
It's easy to feel quite alone when you're starting out; as if it's you against the world. But it doesn't have to be like that. There are lots of courses and support networks out there to encourage people to set up their own businesses, as well as excellent (UK) national and local government resources to keep things as easy as possible.
This is probably the best place to start: https://www.gov.uk/starting-up-a-business/start-with-an-idea. In particular, check out your local support options, e.g. your nearest Growth Hub in England, as well as what is offered by your local council. Plus look for funding opportunities, especially grants to get you started.
I don't pretend that I've got it all sussed; I still find myself running round doing admin and buying loo roll (though we've now got a spreadsheet that proves it's cheaper at Tesco than via Amazon!), but I like to think I'm getting closer to spending more of my time on my key activities of designing and testing new products, consultancy and training...which just has to be more rewarding than doing the shopping!