Through out this guide you will learn how to become a better player with Juggernaut. Farming, ganking, and Partners will be the three topics covered in order to become a better Juggernaut. The three topics will obviously help you with late game depending on your team... looool
*Assuming that you know the basics how to play this guide should be fine and you could fill in the gaps yourself. feel free to leave comments on where i should go into depth
The best partners for juggernaut are those who have one of the following abilities, Stun, Slow, or vacuum. These heroes will most likely help you draw first blood or even a kill when possible. Heroes such as Venomancer, Rylai, Lich King, King Leoric, Slardar, etc. These heroes should harass or give the impression that they will be casting a slow, or some sort of stun to cause the enemy to run back therefore allowing you to farm.
If your partner is harassing you should be focusing on last hitting to rush out your items and denying to cut they enemy exp in half. A good strategy is to follow your partner if they move up to give the impression that you are going to spin but in reality just farm, but if it's possible to get a kill then it is suggested to take a kill and help you farm better obviously. Gaining levels and acquiring basic items such as "Boots" and your "Ring of Health" through the side shop will help you save time instead of running back/ teleporting back/ waiting for courier.
If you have farmed well enough by level 7 and have boots and a perseverance, it's well suggested that you should go gank since you have the perseverance to gank and regenerate the mana back.
If you are not confident in roaming/ganking then continue to do what you were doing in the beginning, rush out your battle fury, boots, and your desolator as your primary items.
Depending on your team you items will vary for the lsat 2 slots such as black king bar if they focus you or they often stun you.
* will be updated when needed or if my guide isn't well focused enough, cheers for now guys