Taking care of many of our physical needs before Shabbat begins allows us to enhance our physical rest and emphasize our spiritual nature on Shabbat.
To prepare, we make or buy the food we will need for Shabbat, clean the house, and put it in order.  The custom is to shower or bath especially for Shabbat.
Before sunset on Friday, we turn on whatever lights we will need during Shabbat so that our homes are well lit. We leave the lights on until Shabbat is over (or we set timers to regulate when the lights go on and off since we cannot be involved with controlling them).