A friend of mine

How do you say:
- A friend of mine told me that...
- One of my friends told me that...

Thanks.

That one is very tricky and is a good question.

Japanese does not have that nuance (that I know of), and that is why when Japanese speak English, French or another language, they will often say :
I have been somewhere with MY FRIENDS / je suis allé quelque part avec MES AMIS
whereas the correct sentence should be with some (of my) friends / des amis .

Similarly, beginners of Japanese will often say : 私の友達とどこか行った　here 私の should not be used, Japanese logic implies that you won't go with someone else's friend.

Here :

- A friend of mine told me that...
- One of my friends told me that...

Click to expand...

will BOTH be rendered simply as : a friend told me that =
- 。。。と友達が言った
- 友達によれば　。。。(according to a/my friend...)

Ok, thanks.
But what if I want to say "Two of my friends"?

自分の友達二人
私の友達ふたり
私のふたりのともだち

自分の友達二人
私の友達ふたり
私のふたりのともだち

Click to expand...

Cheshire, as a native speaker, must be right.
I'd just say : 友達二人 (tomodachi futari) or ふたりのともだち and drop 自分　or　私の ...