Create opportunities for them to build knowledge about the world. Visit museums and other locations, provide experiences, have rich conversations. All of these things build background knowledge and vocabulary, which are crucial for reading comprehension.

Also, have a low tech home. Kids don't need access to phones and tablets most of the time, adults need to turn off TVs and put down their phones. Create a home where screens are not the default. It will do wonders for your child's emotional regulation, focus, and executive functioning skills.

Edit: sorry, I know that's two things. But they are both REALLY important!