Trying to narrow this list down to ten mistakes was a challenging task. However, based on my observations and experiences, these are the biggest and most common mistakes people make when trying to sell anything:

1. Not being prepared when it comes to making a sales presentation, either face to face--as in a retail environment--or over the phone, Skype etc. Being prepared means have all of the information you need at your fingertips, prices, product information, availability - everything.

2. Not looking the part--where the sales person is dressed inappropriately or the entire sales environment looks unprofessional and unappealing to the customer. The customer needs to feel comfortable and safe to make a purchase and a lot of that relates to the look and feel of the sales person and the sales environment.

3. Not having enough knowledge about the products or services being sold. This is a big issue and in fairness to sales people around the world, the rate of product development is making it really hard to keep up. But we have to, because our customers not only expect it, they deserve it.

4. Not asking the right questions. Selling is about communicating and a big part of being a successful communicator is being good at asking the right questions so you can find out exactly what your customer needs.

5. Not listening to what the customer is saying. This goes hand in hand with not asking the right questions and being a poor communicator. Poor sales people never listen to the customer. It's very frustrating to be talking to a sales person and they are either distracted or simply not listening to what we are saying.

6. Not getting back to the customer as promised--or in other words, they over promise and under deliver. We all know how frustrating it is when we have to chase sales people to give them our money. We live in a world with an enormous amount of choice - if you can't follow up, someone else will.

7. Not having clear, specific sales goals. Very few people set goals but those that do tend to achieve them. If you have sales people working for you, you have to set targets. And these need to be talked about, measured and pushed. If you work by yourself, set your own sales goals.

8. Not reading the customer. This means being able to interact with the customer and see that you are connecting with them, that you are helping them and that you are doing your job as a sales professional. Get this wrong and you are wasting your time and theirs.

9. Not being compelling. If you don't believe what you are selling, don't sell it. Being compelling generally translates to being believable and sales people already have a stereotype to overcome. If you don't believe what you are saying, your customers won't either.

10. Not caring about the sale. This is the situation where the sales person really doesn't care if the person buys a product or not. They still get paid the same amount so their attitude towards their customers can reflect this. This type of sales person can cost a business a lot of money.

Every business depends on someone selling something. The better we get at selling the more resilient our business will be. Being a great sales person doesn't mean being a high pressure sales person, in fact it means the exact opposite. It's about being prepared, looking the part, listening, being ready to make a informed and applicable recommendation and most importantly, treating your customers with absolute respect.