The main way is to offer BF at your normal times, and then do solids an hour or so later. That way your LO will take all the milk he needs when he is hungry, and solids are actually just an Activity for now, experiments with new tastes.
In the beginning, solids are just a taste, he probably won't take any real volume for several weeks at least, and even then, pureed vegetables and fruit don't have fats and lots of calories in them like BM does. As he gradually starts to eat more, he will naturally start to take less milk. I really don't think it's something you need to worry about.