It hadn't occurred to me that, at 56, someone might simply assume I was too old to understand something.

I didn't like it much, in truth. I've been helping businesses with social media for more than twenty years, so I'm hardly a 'newb'. More importantly, I've always believed that the principles of sales and marketing remain much the same. The platforms change. The tools change. The technology changes. People don't suddenly adopt completely different human behaviours when they switch between Facebook and Google (well, most people don't, anyway!). Experience gives you a wider knowledge base to draw from. You recognise patterns. You understand why people behave the way they do. All of that informs something as seemingly simple as writing a social media post.

But this isn't really a post about social media. It's about assumptions, and the speed and ease with which we make them.

I learned that lesson in 1997 and I've never forgotten it. I'd applied for a job as an Information Officer at a Chamber of Commerce and had been invited for an interview. When I arrived, a woman in her late teens greeted me at reception and asked me to take a seat with the other candidates.

I joined the row, but unlike everyone else, I didn't sit there quietly. I spoke to the receptionist. I asked how her day was going, made a joke (or tried to) and we chatted. There was no strategy behind it. I wasn't trying to impress anyone. She seemed nice, she looked like she enjoyed working there and, probably, I was nervous. Nobody else said a word to her.

I went into the interview when called. When I came out, I stopped at reception again, thanked her for the chat, made another joke (really pushing my luck now!) and said goodbye. I walked out thinking there was no chance I'd get the job.

But I did.

Later, I discovered that our idle chat hadn't been quite so idle. They had deliberately asked the receptionist to try to engage every candidate in conversation. They wanted to see whether the candidates treated her with respect and what they were like when they weren't sitting in the interview room.

I could have walked in and assumed she was an apprentice receptionist. I could have assumed she wasn't important or that speaking to her wasn't worth my valuable time.

But how could I possibly know who she was, what she was capable of, what her ambitions were, who she had influence with or even how she was feeling that day? Incidentally, she went on to do a master's in business.

Simply being interested, respectful and, hopefully, nice helped me get a job that changed my life. It led to a decades-long career in consultancy and a great deal of happiness. It wasn't a plan. It was simply how I thought people should be treated. Making assumptions about people could have thrown all of that away.

That lesson has stayed with me throughout my career. When I meet someone in business, I try not to assume. I take the time to find out.

In fact, on my very first day in business for myself, I saw exactly the same lesson play out again. I was pitching for a project and had spent some time with the two owners. The woman was sitting near the front door and the man towards the back. The meeting had gone well.

As I got up to leave, the next consultant arrived. He walked straight past the woman, a co-owner of the business, and went to shake hands with the man. I can only presume he'd decided she was the receptionist and didn't matter.

I saw the look in her eyes at that exact moment. I knew I had the job.

So, at 56, perhaps I'm old enough for someone to hold a door open for me and make an "age before beauty" joke. And apparently I'm old enough for someone to assume I couldn't possibly understand social media.

But I'm also old enough to have learned something far more useful: don't be too quick to decide who someone is before you've taken the time to find out.

And let's end where we began, with that fantastic quote from Lemony Snicket, the pen name and fictional persona ofA Series of Unfortunate Events author Daniel Handler.

"Assumptions are dangerous things to make, and like all dangerous things to make, bombs, for instance, or strawberry shortcake, if you make even the tiniest mistake you can find yourself in terrible trouble."