- Relax your body: if you're standing closed off, arms folded with an unfriendly expression on your face, children will respond to that. Place your arms at your sides and try to smile slightly. You might find that children naturally gravitate towards you.
- Say please, thank you and sorry: asking them to give you something? Say please, and thank you if they pass it over. Say thank you if they share sweets with you, and share your own with them. Accidentally bumped their arm on the way past? Say sorry. Model the good behaviour you'd wish to see from them, since it's important to show them that manners carry over into adulthood.
- Answer their questions: if an adult asked you something, you wouldn't ignore them. Well, in certain situations, maybe, but as a general rule, you wouldn't. So, if a child goes "Hello, what's your name?" answer, and ask them what their name is. Always see if you can ask a question back is a very good rule to follow.
- High fives: high fives are my secret weapon. They work as a reward when a child has done something especially nicely, and are a nice alternative to a hug at the end of a visit from an adult they don't know well.
- Talk about Disney movies: even if you don't watch them so much now, your favourite popular one from childhood is a good starting point. They're all still so well known that most children will have heard of them if they haven't watched them. If you do know some of the more recent ones, that's even better. I've had some very nice conversations with children discussing our favourite parts of Finding Dory.
Honestly, I've always thought children respond to me well because I am pretty much still a child in some ways. I think the most important rule is treat them like they are smaller people, with their own likes and dislikes, rather then children as a monolithic block.