Communicating with your contractor is very important. Now that we have the blatantly obvious out of the way, here's a few things that have been working for us.
We all "hate" email, right? Well, it still has a place and time. Even with constant access to email via little devices we carry around all day, your contractor may not actually reply to anything until they have access to a larger device or just after the "work day." Ask if email is a good route for communication. If email isn't, ask what is because you'll probably have to exchange lots of PDFs (plans, product spec sheets, and photos).
Just like with regular folks, some people hate texting and you should figure out if your contractor is one of those people. Texting is fine for a few photos here and there, but unless your contractor is one of them fancy millennials, probably not good for long conversations.
Most smart phones today allow three way calling. Use it. Or if two of you are in the same place, use the speaker. Get everybody in on the conversation.
We're fortunate enough to be able to drop by the house every day at lunch. This has worked out great as we get updates on what happened, what's going to happen, and we get to answer any questions that may have popped up during the day. This has really cut down on delays so far, but we know they'll happen just do to subcontractor availability and material shipping delays. C'est la vie.