Juggernaut is incredibly strong in the laning phase of the game, capitalize on this especially if you have a lane partner with a reliable stun or slow. Simple as run behind enemies, Blade Fury, rinse and repeat until they cry for ganks and refuse to even enter your lane.
NEVER be caught without a TP scroll, as your Blade Fury with grant you 5 seconds of magic immunity to let you safely TP out of a tight situation.
Note: It is important to block, and stay ahead of an enemy while spinning, as it may be necessary to deliver one final slash to get the job done.
You made it this far, good job.
Priority number one is completing your Battle Fury, as it will allow you to farm the jungle with incredible speeds.
Instruct your team that you will be farming and to play defensively, although they will often do the opposite and feed the enemy carry, pray you stumbled upon decent players.
Rack up enough gold for Sacred Relic, pop smoke of deceit and solo Roshan, your healing ward will be more than enough to sustain you.
Now complete Vlad's and get that Demon Edge, your rapier should be completed at around the 30 minute mark.
Don't forget to squeeze Treads in whenever preferable.
Late Game (AKA the period of absolutely no fun for your enemies)
Let me start off by saying NEVER initiate. Sure, you're more than likely the strongest on your team, but this won't do much for you when you get focused and chain-stunned.
The key is playing conservatively, let your team begin the fight, and once you feel the enemies have complete focus on killing your teammates, jump in and deliver them to a world of hurt.
But Johnny, why would you buy an item that drops on death? Aren't you likely to hand it to the enemy?
I wouldn't recommend such a build on anyone but Juggernaut.
Why? Blade Fury.
The ability to evade any form of magic for 5 seconds let's Juggernaut be virtually unkillable in the right hands.
While it does take a good deal of practice to use this effectively, keep in mind, this guide isn't for everyone.
But Johnny, you're not helping your team for 20 minutes!
Once again this build is situational, an opposition with strong pushers will more than likely crumble all your barracks before you can even get half-way to rapier, so in that case this guide would not be recommended.