I gave a best man speech 2 years ago for my friend's wedding and what I found to be helpful was to practice the speech a bunch beforehand so I was comfortable and familiar with what I was saying. Also, another thing I did was treat the speech as if I was just talking to him (making eye contact a couple of times too). This made it a lot easier to ignore all the other people in the room and made me focus on sharing my friendship with him. Honestly made me get so much more into the speech as well and made it more heartfelt. I did have a few blocks and repetitions throughout the speech but just had to keep on pushing. Hope you have a good time at the wedding!