Windows:
1.Create a new folder anywhere and name it Server
2.download bukkit from https://dl.bukkit.org/downloads/craftbukkit/ if its named something else then craftbukkit.jar rename it to craftbukkit.jar
3.open notepad any text software and type java -Xmx1024M -jar craftbukkit.jar -o true
PAUSE save it and name it run.bat place it in the server folder
4.open the run.bat the server will start to stop it type stop in the window it opens

Mac:
1.Create a folder name it server
2.download bukkit from https://dl.bukkit.org/downloads/craftbukkit/ if its named something else then craftbukkit.jar rename it to craftbukkit.jar place it in the server folder
3.open textedit go up to format and chose make plain text
4.type in #!/bin/bash
cd "$( dirname "$0" )"
java -Xmx1024M -jar craftbukkit.jar -o true
5.save it as start.command
6.open it and your done

if this helped make sure to leave a like and check out my server mminecity.no-ip.org