In my over 30 years in marketing, and having provided consulting to hundreds or even thousands of small business owners, one of the most common mistakes I've seen is a...
Lack of Focus on the Core Business
All too often, business owners get distracted with other activities that somewhat relate to the core biz... but actually... they end up staying from their primary objectives.
For example, years ago, I had a consulting client who produced leather goods -- sandals, belts, etc. He was quite successful; however, he wanted to venture into button manufacturing because of the high margins.
So, he had to allocate funds for the button-producing machines, personnel, training, raw materials and other expenses. It was like a new start-up but without the huge upside potential.
Before he knew it, he found himself in a $100,000 hole just like that.
It was a wasted venture... wasted money and time. He found that he had such a strong reputation in the leather industry that the button industry couldn't accept him.
It was a flop.
Had he spent the $100K going deeper into his leather manufacturing business and working on gaining a larger market share, he would have been much more successful.
Is that to say that you can never try something new or branch out? Of course not! But the question you must ask is:
How does this further my core business? And if it's completely unrelated, then be prepared for the challenges (and expenses) that come with it.
"I'd rather have a business that was one inch wide by one mile deep than one mile wide by one inch deep."
That's what it means to focus on your core business: stick to what you're about and take it as deep as you can.