Decide on a folder that everyone will load scripts from. Ideally this is a folder under version control (using e.g. Perforce or SVN), but you can also choose a network folder. As long as everyone has access to this folder it's all good.
Don't do anything to the folder, in a moment you'll create a template startup file by using the installer.
Download the installer and drag 'n drop it onto a Maya window. This starts the installer. Follow the onscreen guides and when prompted to do so choose the folder from step 1.
After the installation you will find a sharedUserSetup.py file in the folder. Commands in this file are automatically run when Maya starts up; it is from this file you will initialize your scripts and tools.
Edit sharedUserSetup.py to suit your needs. It contains initialization examples so all you need to do is extend it to start your specific tools.
Now instruct everyone to run the installer. They simply select the same folder as you did and their installers automatically detect the customized sharedUserSetup file and sets their Maya's to execute it on startup.
Drag the downloaded file onto Maya to start the installer.
Click here to restart your download