A common technique to capture photos of speakers, is low and close with a wide angle lens (35/40mm focal length). It captures the speaker from a flattering angle and from a less common viewpoint, while still capturing the background context. Additionally if possible, to try get a shot of them with slide/context related to their speciality eg. cartoonist drawing, scientist with formulas/subject matter.

For documentation photography, writing good captions is also an important habit and skill to practice.

"Zulkiflee Anwar Haque, a political cartoonist more popularly known by his pen name Zunar, live drawing at an event forum titled "Kleptocrazy Malaysia: Declare Your Assets Now! on May 12, 2017 (Khairil Yusof)"

Captions provides additional context and information about the subject, date, time, event and place. This is something that event photographers will usually not provide. Doing it up front will save a lot of time searching and documenting it later, but also makes it immediately usable by others, including fact checking your photo and who took it.

For a lot of things I do, it's an iterative process, you go back, review and find out if you can do better. Often researching online from more experienced and talented professionals, and if lucky enough, be able to meet them in person and pick their brains with questions about their work and process.

For those interested in getting started in photo journalism or documentary photography, I would recommend paying a visit to Sean Rayford's Youtube channel.

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Additionally, for additional context if possible is to capture the speaker doing something related to their talk or presentation. A cartoonist drawing, a tech person with code, engineering diagrams or device, a scientist with slide of their findings or lab and so on.