1. Setup the basic server files.
   
2. allow the game in your system's firewall
   
3. port forward on your router (for Motorola SurfBOARD routers, leave external ip blank)
   
4. LEAVE IP LINE IN CONFIG BLANK( I will tell you why at the end)
   
5. USE 25565 PORT IF POSSIBLE!
   
6. switch to bukkit/spigot if you want
   
7. add plugins if you want.
   

The reason why you dont want to add your ip in there is becase,
First your traffic on your computer goes through a certain adapter(Like wifi card or ethernet)
for example your main adapter is your wifi card. it has a certain ip on the network like 192.168.1.2
for your network and then the external ip you get from whatismyip.org
by default with the line blank, it uses your default connecting adapter which is 192.168.1.2
so if you put 192.168.1.2, it will try to bind to a connection it's already on.
so if you use a hamachi ip in there it will not get that problem because hamachi adapter is not default
and so its binding to somthing that it isnt already on and using hamachi instead.
Summary of long explaination: IP Line in Config Is For Using A Custom Adapter Instead of your computer's default adapter. (Ex Wifi)