I find it helpful to always remember what the organizer who asked me to shoot wants, and to make a basic shot list, at least mentally, before shooting an event. Something like ...
1. Wide "coverage" shots that set the scene for what it looked like to be there. Widest lens you have, get as high up as you can (balcony? stairs? stand on a chair at least and shoot arms extended over your head using rear lcd), and DO NOT take the shot until the event is at its fullest attendance. If you find a balcony railing to prop on, consider intentional long exposure -- blurred people walking + some stationary people is a neat effect and conveys "busy / well-attended".
2. Next most important is “Presenters” shots. You stand wherever the hell you need to, to get a clean shot of them, as long as you’re not blocking anyone’s view. Get every speaker or presenter, and take more “talking” shots than you think you need, because later when you review your shots, they’re going to be making ugly /unflattering faces in 90% of them. Wait for the punchline, because when everyone applauds they always smile.
3. Participant shots. Long, fast lenses are the best here – the 55 at f4 might be fine with good light. If it’s dark, go 35 f1.4 and get closer. If there’s no LED lighting, you can probably switch to electronic shutter here and you’ll be silent, which helps you not be noticed. Decision: are you a people person? If so, you can choose to tap people on the shoulder who are talking and smiling and ask them to group together and smile. They’ll all say yes. If not, skip it and be a sniper. Watch the faces. People into a really good conversation will be smiling and gesturing, and will also be less likely to notice you… be quick about it. If they look up and notice you, smile, say “thank you!” and move on.
4. Logos… do the organizers of the event have a logo? Is it on display? Put it into shots, nice and clear. They will like it.
Once you’ve checked all these boxes, and you KNOW you’ve got all these in the can, you’re free to experiment. I like to look for symmetry, get that shot framed up, and wait for someone interesting to walk into it. I also like to flatter the volunteers and workers by getting good shots of them hustling and smiling.