Performance feedback to team members/co-workers

As a Line or Project manager you most likely get involved in evaluating people. As Line manager - you need to gather information from other about your direct reports, as a project manager you are often the first contact of a line manager to give feedback about your team.
As a general rule, but not often applied, I suggest that both Line and Project managers should keep some kind of diary where short notes can be added of the team - this way you will have a good draft ready once it is time to make it official.
For Line managers, to get the complete profile do not just ask project managers or people leading your direct reports but also peers and if available, people who is reporting to the person being evaluated. Also, keep focus on open questions instead of Yes/no questions - it is important to get a wide picture before you narrow it done to your perception. When this is done you need to consider what baseline each report is referring from, i.e. are there any comparison.
Key topics to get elaboration on for each co-worker can be used by a line manager when preparing the questions also guidance to whoever get assigned to evaluate someone else.

For project managers, you should take time and keep notes as suggested above otherwise when you are asked you will base your review on very recent events and/or only major events. Remember this another tool to help your team to evolve as well as a good opportunity to sort out what you really need from a team. There is of course a valid point to go through your thoughts with the individual directly, having a healthy dialogue will probably gain some feedback as well.