Screen sharing on a Mac is already pretty easy. Just select the Mac you want to share in Finder, click Screen Share, then log in, but if you're looking for an even faster way, Macworld shows you how.
The process here just requires you to make an alias:
[U]se the method you've used in the past to share the Macs screen... When the [other computer's] window appears take a gander at the shared screen's title bar where it says something like Jim's Mac mini and drag the icon that appears just to the left of that name to your iMac's desktop. A VNC alias file will be copied to that self-same desktop.
That's it. Now you have quick, easy access to screen sharing right on your desktop.
How to create a Screen Sharing Shortcut | Macworld