Before you agree to be a reference for a colleague or friend it is important that you consider what you would say if you are asked to provide a reference. If you have reservations about your ability to write a positive reference then you should decline or at least explain why you have reservations. However, if you have agreed to be a reference then it is important that you get a copy of the advertisement for the position and then carefully outline the skills, knowledge and experiences are required for this job. Then you can begin to think about the skills, knowledge and experiences that the candidate has and how they match with the requirements of the job.
It is important to be able to link the skills to the requirements of the jobs because it will allow you to clearly and concisely articulate these connections. Whether you are asked to comment verbally in an interview or to write a letter of reference it is important that you have planned what you will say. If you seem uncertain or unclear about how the candidate would be able to meet the job requirements, it will come through in the reference. In order to be a good reference for the individual you need to be prepared and aware of the responsibilities of a good reference.
If you feel unable to complete these obligations, you should decline the request to be a reference.