The Ways (or Waypoints or Way Nexuses) are pathways through the Nevernever accessible to mortals.
A wizard can open a gateway to the Nevernever from one location in the mortal world, follow one of these paths a short distance, and open another gateway to a point in the mortal world that would have taken much longer to reach through traditional methods. The Ways may change from decade to decade.
In the series
In Summer Knight, the Senior Council, at Rashid's suggestion, to give Harry Dresden a task in which he must secure the Ways for the White Council through Winter's territories by fulfilling the Winter Queen, Mab's request.
In Dead Beat, Captain Anastasia Luccio informs Dresden about how the Red Court pursued the Wardens in retreat bearing numerous wounded on The Ways through Faerie and had called up Outsiders and demons. Ebenezar McCoy and Martha Liberty arrived to buy time for the Merlin and the Gatekeeper created a large solid shield to block an army of Reds. They are all certain that the Faerie Courts will retaliate against the Reds.
In Turn Coat, when Dresden took a way to White Council headquarters, he was accosted by a group of giant spiders aligned with the Winter Court. According to Ebenezar McCoy, the Council has been harassed several times over the past few months.
In Changes, the Leanansidhe gives Harry Dresden the gem his mother, Margaret LeFay, left him. It holds the sum of her knowledge of the Ways: every path, shortcut, or connection. Margaret developed the skill to predict where they would be in the future. Very few of the Fae can say as much.
Gard opens a way by simply using a rune-carved knife to cut the fabric of reality.
Ebenezar McCoy informs Dresden that Arianna Ortega laced White Council headquarters with some kind of disease. They're not only restarting The War, they're trying to decapitate the Council. With Headquarters out, they lose The Way nexus around Edinburgh making a counterstrike extremely difficult.
Dresden takes his rescue team through the Ways using his mother's jewel. They see some spectacular sights: Nevernever: a menhir with Margaret LeFay's pentangle that she carved herself; Mortal World: Giza where the pyramids are; Nevernever: crystal pyramids that refracted beams hot enough to melt metal; Mortal World: [wikipedia:Machu Picchu|Machu Picchu]]; Nevernever: ten-foot swim in the dark; Mortal World: Mexico.
In Ghost Story, Molly Carpenter opens a Way for Harry Dresden and his ghost army to get into the Nevernever in order to enter Capiorcorpus|Corpsetaker's hideout to rescue Mortimer Lindquist. The Way hung up in the air about six feet off the ground. It's rickety, about to collapse: Bob's doing to keep others from following Harry and team.