This again comes back to the question of whether you are collecting your own debt or collecting for others. Obviously if you have others that are referring business to you, your primary target for advertising would be other business who will also refer business to you. One of the easiest ways to do this is to establish a website.
When developing a website you need to establish a brand and a purpose for your site. Your web site may be informative, sales related, contain marketing material, or simply be a landing page with an opt-in form. It does NOT have to be complicated or complex. When catering to other business, generally, a solid informative marketing website is the most successful. Make sure you have a clear and easy way to get a hold of you. This is generally accomplished via a contact us page or a well posted phone number on your home page. Make sure you have enough information to tell people who you are and what you do. Make it interesting and engaging for the end user so they want to know more about you and your services. Focus your content on what makes you different and what makes your business stand out from your competition. Find your competitive edge and make sure you state that very clear. Social media is also another great way to advertise that you have a new business and service to offer. Make sure you are contributing to blog posts and groups in your market space.
If you own your own debt, you will still want to advertise to others if you plan to grow your business. Use social media networks like LinkedIn, Google +, Facebook, and Twitter, to find others in your market that may have services they can provide. Generally in the debt collection industry, newspaper, radio, mailers, and other traditional marketing means have not proved to be the most effective means. Be creative and create your own online space to advertise your business. Aside from an online presence soliciting businesses directly and leveraging networks and connections that you currently have prove to be the most fruitful.