The personality of the person that you choose is probably more important than anything else. You want to choose someone that will fit in with you and represent your company ell. Consider how they will come across and how their personality may be reflected in their work. Ideally you want someone that is committed to what you are doing, is positive, forward thinking, ambitious, hardworking and respectful. This may not be easy to find, but you will find people out there that are like this, you just need to look really hard and be prepared to keep searching until you find them.
Obviously you will need to consider what skills your employees have. Think about whether you would rather they had certain skills or whether you would prefer it if you taught them the skills yourself. If they already have skills they may not be doing things quite the way you like, but training them yourself will mean they will learn to do it your way. Of course, you may be looking for specific skills that you do not have that you wish them to have so that they can fulfil a certain role. Think hard though about all of the skills you would like them to have, not just the main ones that you need.
It is really important that customers get treated well by all members of staff. Even if the role is not directly customer facing, there is always the chance that they will communicate with customers and therefore need to be able to be skilled at doing so. Being friendly, positive and helpful are therefore really important. It can be good if they have had previous experience of customer service it can be useful, but do not assume that previous experience means that they are good! Just because they have done it before does not mean that they have been well trained or have an understanding of how important it is to be good with customers.
Obviously cost will be a big factor for a lot of employers. You will have a budget and therefore will need to find someone that fits in that budget. This could be high or low, but you still need to find the person that provides the best value for money. Therefore make sure that you interview a lot of people and if you are not sure, interview them again so that you know that you will be getting the best person that you can within your budget.