(1) What sorts of interview questions do you find are most frequently asked? I think probably the most common question I was asked the last time I was looking for a job was to describe the singleton pattern.
(2) What sorts of interview questions do you find are most useful to determine the merit of a job candidate? I would guess the answer to this might be different...
I believe that the basics are asked everywhere no matter what level of experience one has. Also the sort of questions depends on the type of job one has applied for and the knowledge of the interviewer also.
Yes as Reehan indicated, fundamental questions are always asked and that is why I have marked popular questions with a "FAQ" icon meaning "Frequently Asked Question". Also I have categorized the questions in to 14 key areas like Java langauge fundamentals, J2EE specification fundmentals, Performance issues, Threading issues, Transactional Issues, best practices etc. These are the areas technical interviewers like architects, senior developer etc will be interested in.