This post is based on these instructions:
http://www.wuppy29.com/minecraft/modding-tutorials/wuppys-minecraft-forge-modding-tutorials-for-1-7-releasing-your-mod-standard-setup/
The main steps are:

1. Edit build.gradle and change the group and archiveBaseName entries
2. Run gradlew build
3. In the folder build – lib, you will find your Jar file: you can post this on a website for other people to use.

To install Forge if you don’t already have it installed:

1. Download it here: http://www.minecraftforge.net/forum/index.php?action=files
2. Look for 1.7.2-Recommended and then click on Installer-Win
3. Select “Client install”
   1. You will end up with a new Minecraft profile called Forge
   2. Select this to run Minecraft with Forge

To install your new mod (or any Forge mod):

1. Open Windows Explorer and enter %appdata% as the location
2. Open the .minecraft folder and then the lib folder
3. Copy your new mod Jar file into lib

Next time you run Minecraft with the Forge profile, you will see your mod.

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