The Git way - For windows users

Use following settings in options, read more here.

Windows Explorer Integration -> Context Menu Entries -> Gut Bash Here + Git GUI here
Run Git and included Unix tools from Windows Command prompts
Checkout Windows style, commit Unix-style endings

Navigate to: C:/Users/YOURNAME/Documents (Note, always use forward slashes "/" for compatibility)
Right click in folder -> Select: Git Gui -> Clone Existing Repository
Source Location: git://github.com/Pymol-Scripts/Pymol-script-repo.git
Target Directory: C:/Users/YOURNAME/Documents/Pymol-script-repo

You now have all the scripts available in your directory.

You now have to add the "Pymol-script-repo" directory to the PyMOL search path.

import sys
sys.path.append('C:/Users/YOURNAME/Documents/Pymol-script-repo')

Save under: C:/Users/YOURNAME/pymolrc.pym (Set: "Save as type" to "All files")

Now start PyMOL, and test in PyMOL.

print sys.path
import colorbydisplacement
help(colorbydisplacement)

Get latest changes to scripts

If new scripts are available or changes have been made, then:

git pull origin master

sudo apt-get install git

git clone git://github.com/Pymol-Scripts/Pymol-script-repo.git

You now have all the scripts available in: /home/YOURNAME/Software/pymol/Pymol-script-repo

You now have to add the "Pymol-script-repo" directory to the PyMOL search path.

gedit ~/.pymolrc

Write

import sys
sys.path.append('/home/YOURNAME/Software/pymol/Pymol-script-repo')

Save and exit

Now start PyMOL, and test in PyMOL.

print sys.path
import colorbydisplacement
help(colorbydisplacement)

If new scripts are available or changes have been made, then:

git pull origin master

Now you are done.

Information how to contribute scripts to the repository. It's easy!
http://www.pymolwiki.org/index.php/git_authors