In the old days when people studied traditional grammar, we could simply say, "The first person singular pronoun is "I" when it's a subject and "me" when it's an object, but now few people know what that means.
Let's see if we can apply some common sense here.
The misuse of "I" and "myself" for "me" is caused by nervousness about "me." Educated people know that "Jim and me is goin' down to slop the hogs," is not elegant speech, not "correct." It should be "Jim and I" because if I were slopping the hogs alone I would never say "Me is going... " So far so good.
But the notion that there is something wrong with "me" leads people to overcorrect and avoid it where it is perfectly appropriate. People will say "The document had to be signed by both Susan and I" when the correct statement would be, "The document had to be signed by both Susan and me."
Trying even harder to avoid the lowly "me," many people will substitute "myself," as in "The suspect uttered epithets at Officer O' Leary and myself." "Myself" is no better than "I" as an object. "Myself" is not a sort of all-purpose intensive form of "me" or "I."
Use "myself" only when you have used "I" earlier in the same sentence: "I am not particularly fond of goat cheese myself." "I kept half the loot for myself."
All this confusion can easily be avoided if you just remove the second party from the sentences where you feel tempted to use "myself" as an object or feel nervous about "me." You wouldn't say, "The IRS sent the refund check to I," so you shouldn't say "The IRS sent the refund check to my wife and I" either. And you shouldn't say "to my wife and myself." The only correct way to say this is, "The IRS sent the refund check to my wife and me." Still sounds too casual? Get over it.
On a related point, those who continue to announce "It is I" have traditional grammatical correctness on their side, but they are vastly outnumbered by those who proudly boast "it's me!" There's not much that can be done about this now. Similarly, if a caller asks for Susan and Susan answers "This is she," her somewhat antiquated correctness is likely to startle the questioner into confusion.