As a child I used to stutter when reading aloud to myself. Practicing by reading whole books aloud helped a lot. Some books were more difficult than others, especially those with really weird sentence structure, or really short sentences, which used to get me out of the flow.

With practice, I stopped stuttering when reading aloud altogether, and then even when reading to other people (family members first). Talking to people however it's completely different matter, and it's still hard for me.

I think there's some common difficulty curve. For me, things that became easy with time (even when I've stopped practicing by reading aloud) are, in order: reading aloud to myself, talking with siblings and parents, reading aloud to others, explaining technical matters to friends, talking to younger colleagues, and lately talking to friends, even on the phone.

Talking to strangers is still difficult. I also find it gets harder the more unexpected is what I'm trying to say (for example, saying "sorry, I couldn't hear you, could you repeat that please?" instead of answering a question).

Partially related: there's a /r/Stutter subreddit (which I haven't opened in years), if you want to read about some other people's experiences.