If a large solar flare were to directly hit the Earth, it would significantly affect all of the electronics on Earth. Us being so dependent on electronics, this would be crippling to essentially all forms of communications, payment and many other important functions of life. Most cars would shut down due to many new cars having electronic transmissions. The giant solar storm hitting Earth would be one massive electromagnetic pulse, first hitting all satellites which would knock out communications, and then moving on to all the electronics on the surface of the Earth. Luckily, we have preventative systems in place to warn us several days in advance if something like this were to happen. NASA has a satellite designated to report any activity that would hint at the possibility of a solar flare hitting us directly, so we would have several days to prepare. Things we would do to limit the effects of these solar flares would be things like shutting down satellites and shutting down transformers. If we were to not predict an event like this several days in advance, after hitting the first satellite we would have about thirty minutes before the solar storm reached the Earth. For a more detailed and visual description of the possible effects of a solar storm hitting the Earth, reference this video.