From my experience, the best way to create personas is to conduct interviews in the field with participants who represent the customer or actual user of the project, service, website, etc. that you are looking to design. In preparing to do this type of work, it is often best to ensure that one takes the necessary steps before beginning the interviews.
Recently, we had the opportunity to work on a persona project for a client who was redesigning their website. Before heading out into the field to conduct interviews with participants, we held a strawman workshop with the key stakeholders. The benefits of holding such a workshop include:
1) Gaining Buy-in: For some, creating personas in the first place is a new concept. As a result, it helps everyone to get together and agree on where we are starting from and where we are headed.
Everyone has a picture in their mind of who their customers are. These ideas come from a variety of sources. It is best to get these all out in the open before you head out into the field so that you can validate them with research. Sticky notes help participants generate these ideas collaboratively.
2) Increases Interest: Once the stakeholders have helped to create draft personas, they will be very interested in the results from your field work. They made assumptions about who these personas are, and they would like to know what held up. What lined up with their assumptions? How far off were they?
3) Increases Focus: During the strawman persona workshop, areas of debate are likely to arise. These will be important to add to your research guide, and it helpful to know the areas of controversy before you begin your interviews.
On a final note, getting all of your key project stakeholders in a room to meet for this type of workshop can be difficult. Be sure to schedule these with as much lead time as possible.