Listen people, this is easy: you do not always use the word "I" when speaking of yourself and another person.
I'm going to be called a grammar Nazi for devoting an entire weblog entry to this, but it's driving me crazy. Over the past week I've seen this error a dozen times, and from smart people who should know better.
What am I talking about? We're taught from a young age that it's polite to say:
Jane and I are going to the store.
That's well and good for the nominative case, when you and Jane are the subjects of the sentence. But it does not work if you and Jane are the objects of the sentence. This sentence is an abomination:
The man gave ice cream to Jane and I.
This is WRONG, and it hurts my brain. It's like fingernails on a chalkboard. I'm serious. It drives me insane. Would you say this?
The man gave ice cream to I.
Of course not! Politeness does not take precedence over grammar. The proper sentence in this case is:
The man gave ice cream to me.
And if you're talking about yourself and another person, then the proper form is:
The man gave ice cream to Jane and me.
I know that sounds wrong, but it's better than "Jane and I". Far better. And if you really want it to sound better, then ditch your notions of the polite and say:
The man gave ice cream to me and Jane.
However, the real answer to your dilemma is to use the handy clear and concise first-person plural.
The man gave ice cream to us.
Isn't that nice?
Are you confused? Here's an easy way to tell whether you should use "Jane and I" or "Jane and me". Ask yourself: if this sentence were only about me, which would I use, "I" or "me"? Use the same pronoun when talking about yourself and another person. Seriously. That's the rule.
You make Kris and I weep when you do this.