I see a lot of neurodivergent people talk about small talk as this baffling and meaningless waste of time that neurotypicals do for some unknown reason, and as an autistic person in an industry that is extremely based on building relationships and engaging with others, I've actually found a few really key important pieces to small talk.
1. Small talk can make interactions feel less mercenary or transactional. Having even brief exchanges about something beyond the reason that you're interacting can make it feel less like the only goal of the interaction. Especially for relationships that are not fully transactional (e.g., coworkers), this can help build a relationship with them.
2. Small talk can be a way to find commonalities and help bridge cultural or power divides. Recently I was on a call with a couple of Indian colleagues, and while we were waiting for everyone else to join I asked them where they lived in India. They didn't expect that I had heard of it, but I knew it because my dad had traveled there for work every couple months for a year or so, so we could chat about it briefly. Even for a couple of minutes, we were able to connect on this unexpected commonality. If I hadn't had that connection, I would have been able to learn about somewhere, helping narrow the privilege gap of them being expected to know more about where I live than I am about where they live.
3. Small talk can show knowledge about a person, which both builds connections and indicates that you see their life as important enough to remember about. The stereotypical "How's the wife?/How are the kids?" shows that you know the person has a wife/kids and have enough interest in their life to even ask.
4. Small talk can ease tension and reduce pressure from others, especially in a professional setting if more junior members are expected to speak. Especially for junior staff members, it can be difficult to be the first person to talk and break the silence, so engaging in small talk beforehand allows for a lower-pressure transition from silence to whatever the presentation is about.
5. Small talk provides a low-risk way to identify commonalities. While conversations about religion, politics, etc. may lead to tension or discomfort, even if they bring out commonalities, small talk is specifically structured to minimize tension while still providing the opportunity to learn more about each other. A conversation about the weather can reveal that you both like hiking when it's nice out; a conversation about the weekend can reveal that you both have family in the same state.
Small talk in many cases is signaling, a way to indicate certain things to people. It's a more indirect version of it than many autistic people like, but it is one.
But, you cry, I don't know how to do small talk!
Small talk actually has some pretty clear guidelines, even if they are often unspoken.
You are generally always safe starting with a question.
Weather, traffic/travel, and non-political events are generally a safe bet, because those are commonalities even if you are in different locations. "It was so nice out here this weekend. What's the weather like near you?" "I got stuck in that big traffic mess on my way here. Did you get caught in that?"
If you have some knowledge about that person, use that to inform further questions. I knew my coworkers lived in India, so I asked where in India. If I had just known that they didn't live in the same country as me, I could have asked where they lived.
Let them offer information about their family before you ask about it. Family can be complicated, and if you wait for them to offer that will indicate what sort of information they are comfortable sharing. You can then mirror their language (e.g., if they mention a wife then you can ask how their wife is doing, if they mention a partner then you can ask how the partner is doing). If "how are they doing" feels too personal, language like "what are they up to these days?" can be a bit more neutral and feel less invasive. If you're really not sure, feel free to avoid questions about family altogether.
When asking about where someone is from, don't ask "where are you from originally?" unless you know for a fact that they are not from where you are. Instead, you can ask things like, "Did you grow up around here?" which is a more neutral phrasing. This is especially common for the area where I live where a huge percentage of people are transplants (including me) and so people who actually grew up in the area are a bit of a rarity.
Politics, religion, and money are generally not good starting points for small talk
Weather, traffic/commutes, non-political events, and weekends/time off are generally safe bets
