Mistakes made with the English pronouns I and me have been increasing exponentially for years. The difference is actually very simple – let me explain it to you.
I is the first person singular subject pronoun, which means that it refers to the person performing the action of a verb.
Me is an object pronoun, which means that it refers to the person that the action of a verb is being done to, or to whom a preposition refers.
The Bottom Line
This confusion usually occurs when you have I/me connected to another pronoun or name with "and" or "or." I believe that the confusion begins when someone says something like "John and me are ready" and that is corrected to "John and I are ready." The speaker then thinks, "Oh, the word ‘and’ means that I should always use I." This is not the case. "And" has nothing to do with it; the reason you say "John and I" in that sentence is that "John and I" are the subject. If they were the object, you’d use me: "He told John and me to get ready."
If you are not good with grammar concepts like subject and objects, there is still a very easy way to decide whether to use I or me: try out the sentence with just I or me (or if you need a plural, we or us – "we" is equivalent to "I" and "us" is equivalent to "me."):
And whatever you do, please don’t use a subject pronoun and object pronoun together!