Click two buttons to get to navigation screen
You can do a single swipe right from the menu icon to open navigation.
Now another little box pops up with three options; send, routes and go
Click on go
Here it's actually already started navigating, and you can just let the dialog time out to go away, you don't need to click Go if the audio is enough. If you need to see the screen right away, then you do need to click "Go".
Minor stuff, but it saves a couple of clicks.
One warning about optional routes that's not made clear, if you select from the list of alternate routes suggested, then Waze will not attempt to redirect you if traffic conditions change, and if you leave the route Waze will try to get you back to that route. Of course during the drive if you think conditions might have changed, or you've started to go a different way, you can get a new list of alternate routes but again the same things will apply when you select one. The default route that it selects for you may or may not appear in the list of alternate routes, but the default one is the only one that Waze will attempt to fine tune as you are driving.
in my own personal experience, I've found Waze to be pretty unreliable for long distance routing in the US. If you go through areas with limited cell coverage, or lower population densities, then Waze will not have accurate speed information and you may encounter map problems that generate really bad routing. Waze works best in heavily trafficked areas because errors are found and corrected quickly. I would recommend having at least one alternate GPS solution if you are going to use Waze for long distance routing.