Hi, i'm 28 years old, and i'm not a parent with a slow talking kid. I'm an adult who was slow to talk as a kid :)
I have mild autism, but i have an expressive/receptive language disorder. I struggled to speak till i was about 4, then it improved. It improved through my mum encouraging me to read, and sing along to songs, and it does really help, even now. I think without that, i would be a lot worse. At school, i had problems with it, but it wasn't diagnosed, so i was just told that i wasn't concentrating properly. I was concentrating, it just took me a while to understand things.
I think you shouldn't worry if you're kid is a little slow to talk, it's very common. But if they get to school age and they're still struggling, then it's time to intervene. Things, you can do to help, is reading to, and getting them to read along (look for the puddle lane books, they're very good for that) and get them listening to songs and sing along to them (even if they're tone deaf lol)
Any questions, then just comment :)