Whatever your business, there is always competition. Before you start up a business, make sure you have checked out all the potential competitors.
This means indirect as well as direct competition. Direct competition is usually obvious: a new plumbing business will be in competition with all of the other plumbers in the area.
You might have to think more laterally to identify the indirect competition. For example, a new flower shop on the high street should view the Thornton's chocolate shop as a competitor; the Italian restaurant has competition from the local cinema. In both cases, they are 'chasing the same buck': in the first case it's a gift and in the second it's a night out.
Your business plan, then, should take account of all the possible competitors. Having thought laterally to identify them, continue thinking in the same vein to work out how to persuade potential customers to spend their buck with you.
For example, the Italian restaurant could consider a cheap early evening menu to capture theatre and cinema-goers without taking too much more of their hard earned cash.