If it's a freelancer you're after, be sure to ask for examples of work from any prospective freelancers regardless of the project; this will allow you to assess their level of professionalism - a talented freelancer should be chomping at the bit to show off a portfolio of work to would-be employers, as well as testimonials from satisfied clients.
Rigourous vetting is all well and good, but it's impossible to truly gauge someone's capability until they're working on a job. If you're slightly skeptical, it's best to start by offering the freelancer a small project of a few hours so you can better evaluate their capabilities for a larger one. It isn't absolutely necessary, but it does help if a freelancer has a proven track record in the discipline you need. It's also wise to ascertain whether they've completed similar projects to the one you're looking to have carried out.
Having a clear brief is vital and regular communication crucial, particularly if your freelancer is based at home and not in the office, as 90% are. While you might not be able to plan every aspect of the project in advance with the freelancer, make sure you set out any key deliverables at the beginning, as well as agreeing on deadlines and points of contact. The nature of the project will determine whether you will need to take a more hands on/hands off approach and, how much of your own time you are willing to devote to steering it if necessary. Rather than allowing a project to spiral out of control in a direction you're unhappy with, be brutally honest - let your freelancer know if you expect a higher standard of presentation, more depth in a piece of research, etc.
A good employer should recognise that they have a duty of care towards a freelancer, just as they would for any other staff member, be they permanent or temporary. It's a good idea to be as available as possible to give advice and feedback to a freelancer, particularly if they are unfamiliar with the culture of your organisation and its values or policies. Apprising them of codes of conduct is also a must, particularly if you have any email or computer usage agreements - it's your reputation on the line otherwise. And if you're working with a freelancer who is based at home, consider whether you need to draw up a contract about place of work.
The modern freelancer is often very active on Twitter, Facebook and other social media channels; if you have any major concerns about the confidentiality of your project or company, be sure to raise these with the freelancer. It's important that they are made familiar with any social media agreements or contracts prior to working with you. It's a great idea to get your freelancer to sign a non-disclosure agreement, and with a multitude of templates available online, it's never been easier to ensure confidentiality. Equally, if you do want to promote a great piece of work your business is working on, it can be highly beneficial to have a seasoned social media pro on hand to boost your profile.
Finally, if in any doubt - go with your gut instinct!
Xenios Thrasyvoulou (pictured) managing director, PeoplePerHour