Sometimes I tell them up front, sometimes after I stutter. It sucks because my stutter comes out at the worst of times like when I'm introducing myself (I have blocks for my name which is annoying). However, it is a low/moderate block/stutter so sometimes it just seems like I'm just taking my time to form a sentence. Sometimes I use the excuse of finding the right word in English when I'm trying to find a synonym for a word. My friends don't really give me any special treatment besides not talking over me but that's also because of mutual respect/politeness. I'm really extroverted and if I have a block or stutter, they just let me get the sentence out and the dynamic of the convo isn't affected too much. I feel like for me it is just how you carry yourself? Not sure if that makes sense :-)