Hitching to Yellowknife
If traveling from Edmonton, Alberta, there are several highway options that will take you towards Yellowknife, with the most recommended being by way of Hwy #43. To access this Hwy, travel westbound on Hwy #16 to just west of Stony Plain, and then take the Hwy 43 exit ramp North. There is a turnout within 1km of this junction that offers an ideal place to hitchhike from. Hwy 43 is the main truck route, and so your odds of being picked up by a big rig that is going all the way up to Yellowknife is high. Carry a sign that says NWT or Yellowknife to better your odds of a lift.
To get from Edmonton to Stony Plain, try hitching with a sign, or taking the greyhound as it is a very short trip, but can sometimes be tricky getting out of Edmonton.
Once Northbound on Hwy 43, you will eventually hit the town of Valleyview, Alberta which is where the highway forks, and you can either continue North-West on what is the Alaska Highway or North on the Mackenzie Highway. The most direct route to Yellowknife is via the "Mackenzie Highway".
If hitching in the summer, be prepared for swarms of black flies, horseflies and mosquitoes, as well be aware that there are many black bears in the area and it is not uncommon to see them. It is not recommended to opt for rides that will drop you off on a desolte stretch of highway, its safer to start and end legs of your trips in communities or at the very least, near a gas station. There are a handful of stretches where there are no communities or gas stations for several hundred km's, and these are terrible areas to be stranded. Be sure to carry adequate food, water and a tent/sleeping bag.
Also, for summer travelers, be aware that there is a ferry crossing at the Mackenzie River, roughly 315km south of Yellowknife. There is no cost for the ferry, and it runs from 6am - Midnight seven days a week. If traveling Northbound, the last ferry crossing is at 11:30pm, and if traveling south, 11:45pm.