I love my children, but I am not always sure about other children. It's not that I don't like them, it's that I am not always sure how to communicate with them the right way. I am always afraid of treating them as if they were too young or too old for their current development. It sounds like a silly fear, but it does mean that sometimes I don't know how to little kids other than my own. I have learned that if you let them do the talking first, you will know what to say and what they want to hear. It becomes a matter of listening first.
Little kids have varied interests. Some like dinosaurs and some like trucks. Some kids like to play in the mud and some would rather host a tea party with their friends. However, if you remember the one interest that they all have, you are going to know how to communicate with little kids in a much easier manner. Their main interest is themselves. That does not mean they are self absorbed in a bad way, this is just the nature of childhood. They grow out of it, mostly, but kids are really interested in talking about what they are doing. Remember that and you can talk to anyone.
Perhaps the key to talking to little kids is to see what they are doing, and then ask them about it. They are going to be more willing to talk if they know you are interested in them. When you meet your friend's little ones for the first time, for example, they may be shy because they don't see you a lot. Some children are very open and will talk to you no matter what, but you may have to work a little more with little kids that are more shy and unsure of adults they do not know. Stranger anxiety is typical with many age groups, and is actually a good thing to keep them safe, but it can make things awkward for you.
Remember when communicating with little kids that are not your own, there are worries that you should consider. If a child that does not know you very well is willing to tell you anything and wants to go somewhere with you, you may want to talk to their parents. It is hard to teach little children about stranger danger, and if you see a child that is very willing to be led away, and you know the parents, you may want to tell them. Some children think that if they know someone's name, they are no longer a stranger. It's hard, but some kids are more willing than others, so be careful what you do.
If you are going to be babysitting these little kids, you do want them to have some trust in you. This is going to be something you work on with the parents. The parents have to make it clear that they trust you and that it is okay for them to be with you when they are not around as long as Mom and Dad know about it. Don't be disheartened if they are resistant, as that is a good thing for them. Little kids can be complicated, but they are also a great source of joy, even if they are not your kids. You can learn a lot from their very open and unbiased declarations.