“My friends and I” is grammatically correct when it is placed before the verb and is the subject of the sentence.
“I and my friends” is also correct but less common as it is more polite to put your friends first.
My friends and I are going to the cinema.
The most important thing to remember is that “I” is the subject pronoun(the person that does the action) and “me” is the object pronoun(the person that receives the action. You can read more about subject and object pronouns here.
When “Me and my friends” is incorrect
“Me and my friends” is incorrect at the beginning of the sentence but it is common to hear people saying it all across the English-speaking world.
People tend to make this mistake as the subject includes more than one noun.
We are so used to subject(I) + verb that when this structure is disrupted, it can be easy to make a mistake.
I remember being corrected as a child that it is always “my friends and I “ and finding it difficult to say this structure. It is much easier to say “me and my friends” and for that reason, we often make this mistake.
I play tennis.
Subject verb object
She loves me
My friends and I play tennis
When to use “Me and my friends”
“Me” is an object pronoun that means that you receive the action.
He punched me.
In this example, you received the punch. It doesn’t make sense to say “me punch”.
You can only use “me and my friends” when you and your friends receive the action.
They started a fight with me and my friends.
The artist painted a picture of my friends and me.
Again, it is just a form of politeness to put “my friends” before “me”.
Grammar and writing are difficult and I recommend you read my KoalaWriter review next.