Often a quick UI evaluation needs to be done without actual users’ involvement. What approach is to take?
Is there a framework one could stick to (i.e. principles to look out for, steps to take as part of the evaluation) or is it all haphazard, art based on experience rather than rigid process?
I personally find that the only way to properly evaulate the effectiveness or usefulness of a UI is to get feedback from the users, as they are the ones that use the application.
If this is NOT possible for some reason, VERY solid specifications are a great place to start with the investigation of proper UI completion.
I'm not sure about an actual framework (I agree that users are necessary) but a lot of time the UI can be checked at a high level against Jakob Nielsen's usability heuristics which are time tested.
In some products that plugin into specific environments (e.g., Eclipse based product), the hosting framework often has its own usability and UI guidelines. That obviously doesn't cover everything but it is a good start.