Me or I

How do you know whether to use 'me' or 'I'.
Consider this sentence:
My mother and I talked about my sister and me.
I'll tell you a trick about this 
Take the first part of the sentence - My Mother and I , drop the words 'My Mother' and then use it with the verb 'talked' 
Which sounds correct 'me talked' or 'I talked' ? Obviously 'I talked'  so you go for 'My Mother and I'. Then let's look at the second part of the sentence- 'about my sister and me' . Now drop the words 'my sister and' and look at the sentence
'My Mother and I talked about me',
now check it out with 'I'  
'My Mother and I talked about I'
'I' sounds distinctively out of place here.
That's how you can decide and you will never go wrong.