Best Method for Following a Route While Cycling?

Bike with a buddy that can follow instructions.  Perhaps a female buddy cause we know males don't like directions. 

Has anyone followed a pre-uploaded route using a 910XT?  Good?

This is always a problem for me as well.  I used to print out and even laminate turn-by-turn cue sheets and attach to my bars.... but without my reading glasses, I can't figure out what's coming next.

Now, I pretty much just stop and pull out my iphone periodically and figure out where.    

If you have an iPhone you can just set it to never auto-lock for your workout. It does eat up your battery pretty quick that way though, turning your back-light brightness down will help though.

I have a mount for mine that basically puts the phone on top of the stem and then I use Map My Ride and it shows me where I am and where the route goes.

A Successful ride

This.

You can also get battery extenders compatible with bike mounts like the one by wahoo fitness.

I draw a map (rather than a cue sheet) and refer to it if I really need it, it's probably not the "best" method, but I find that people become overly dependent on GPS.  I will occasionally get lost, but I've had some fun rides and found some great roads that way.  If you are riding somewhere away from home though, its probably best to have some sort of navigation, and even actual maps in case you have issues with your tech.

This.  Put it in a ziploc in case it rains.  Also, keep a separate sheet in your saddle bag if you're afraid of getting lost (you may lose the one you're using).  I've used this method for rides up to (and over) 600 miles long.  Of course, you can use GPS, etc., but this works fine.

My experience exactly.  And as another poster said, ALWAYS ride with a ziploc baggie.

How complicated are these riding routes?

If I'm going somewhere new and complicated I'll tape a cue sheet to my top tube, and if I happen to wander off course I always have my phone to check to get back on course.

I have an absolutely abysmal sense of direction and I always manage to find my way around... is it really that complicated?

How big are they for you? 50+ lines to fit in isn't really unusual for me around here, so having it on a device (Edge 800) is kind of nice. There just aren't many sections of road where we can do mile after mile up here. And I'm actually curious because from what I know of the general area the road crossings are spread much farther apart.