How to create your first archlinux package with PKGBUILD

Question

I am trying to make something really simple. A simple hello world program that's installable as a package for arch. So i've tried to create a PKGBUILD file but i couldnt figure it out on how to package it. What i want to accomplish is:

1. Grab my repo from github
2. Compile the file/-s
3. Create a system variable so that i can run it from anywhere with a predefinded keyword
4. (optional) checking with gpg

And i want to generate a package that i can install using sudo pacman -U helloworld-1.10.tar.xz

I hope someone could help. Any help would be very good to have. Thanks :-)