grammar - When do I use "I" instead of "me?"

From some comments in the answers for common English usage mistakes (now deleted, 10k only), there's confusion around the usage of I vs. me:

While the sentence, "the other attendees are myself and Steve," is agreed to be incorrect, there's confusion about whether the correct form is "the other attendees are me and Steve" or "the other attendees are Steve and I."

(I've always used the heuristic of removing the other people from the sentence, so I always thought "the other attendee is me" would be correct, instead of "the other attendee is I." Is this true, or am I using a flawed heuristic?)

Answer

Your method of removing the others is indeed correct. At least, that is what I used to do when I was in high school.

Always try using "I" or "me" in the singular, for the same sentence. For instance, people might say:
"Robert and me are going to town." Which is wrong, because one does not say "Me am going to town." Therefore the correct way to say it is "Robert and I are going to town."

However, this sentence is also wrong: "The police arrested Robert and I", because if it were in the singular, one would not say "the police arrested I", it is, "the police arrested me." Therefore one should say, "The police arrested Robert and me."