If you are a business owner and are looking to recruit new members of staff then you need to consider where you are going to advertise the job. It may be that you need to take on someone very quickly in which case you may decide to advertise in as many places as possible. If you are in no rush then you may try advertising on your own website or in a local paper first before venturing out to other avenues.
You may decide that you have not got the time or resources to advertise the job yourself fand outsource it to an agency. If you are going to use an agency then you will have to expect there to be a cost involved in advertising and managing the whole job application process for you. Often agencies will ask for a fixed fee or a percentage of the salary that you are offering on the job as their commission.
If you are advertising the job yourself then you need to consider where you wish to post your ad. Social media sites such as Facebook and Twitter are a great place to advertise jobs and get your post seen by thousands of people.