Think about the process of purchasing a product, signing up for a service, or embarking on a holiday.

What's the first thing you would do? Look it up online, right?

The next step would be to check out the reviews, maybe on Google, Yelp or popular travel rating site TripAdviser. This could change your entire itinerary, shopping list or business plans. A good write-up may confirm the wisdom of your planned purchase but a slam is likely to make you think twice.

But how seriously can you take negative reviews?

Take travel. In days gone by you would ask a friend or family member who had visited the location or attraction what they thought. Then you'd balance their feedback against what you know about them: Are they overly enthusiastic or miserable sods? And can you trust their judgement to be wholly neutral?

You can't do that with the internet. All you have to go by is the one-off review, often with no evidence of the user's actual experience.

As someone who works in the PR industry, my agency was writing about this and teaching clients how to deal with it over six years ago. If anything, the problem has got worse since. If you're a retailer or owner or service provider, it's difficult to deal with and even if you try to take it on, it can backfire.

In fact, it's doubly difficult because those who have a positive experience on a visit or shopping trip don't leave a review. Those who didn't enjoy themselves, on the other hand, are more motivated to bang out a few paragraphs of criticism. After all, who wouldn't want to take revenge over poor service? With leading data analysts saying 67% of people trust online reviews as much as personal recommendations, it's important to know how to tackle a negative review.

Recently, an Edinburgh-based fish and chip restaurant refused a father and his daughter access to the bathroom. The father then urged his friends and family to leave negative reviews and within a day the eatery shut down its social channels in an attempt to manage this. (Wrong move. You should always deal with this head-on.)

It's not just small restaurants that are at risk of harsh feedback. Leading Scottish attractions can also fall victim to the amateur critic's pen.

Consider Edinburgh Castle. It's one of Scotland's top tourist attractions, but not everyone sees it that way. Of over 20,000 reviews, 111 are marked as terrible. Let's look at some of them.

One user blasts the views as "not the greatest" and goes on to complain about a hair being in his cake. With no photograph provided, the claim can neither be verified nor rebutted.

Another blasts it as being too full of tourists. (Perhaps it would look better if it was empty.)

It's not only Edinburgh Castle, though. Kelvingrove Art Gallery and Museum receives the treatment too.

The commenter discounts the top attraction as both "boring" and "good". Which is most helpful.

What about Scotland's highest peak?

"Not actually that tall". So don't worry about travelling to Fort William. There are some real corkers around this particular attraction but it's worrying that people are served by these reviews.

Our final attraction is the UK's number one visitor site: The Royal Yacht Britannia. As the former vessel of a monarch it attracts quite a lot of attention and even gets some reviews objecting to its very existence.

Someone says they thought about asking for their money back. However, in a brave move the attraction's marketing manager responded directly to the criticism:

Now, if you're a business owner you obviously can't respond to every single negative notice but you should bear in mind these key tips:

I'm a sort of collector of these negative reviews and brilliant replies. If you spot any please do send them my way at @kennymurray.

Kenny Murray is a digital strategist for Edinburgh-based public relations agency Holyrood PR. His specialisms include social media and data analysis. Follow him on Twitter at @kennymurray.