Ready to upgrade to Yosemite? First thing to do is make sure your hardware will support the upgrade. From Apple’s upgrade page, here are the eligible models:

• iMac (Mid 2007 or newer)
• MacBook (Late 2008 Aluminum, or Early 2009 or newer)
• MacBook Pro (Mid/Late 2007 or newer)
• MacBook Air (Late 2008 or newer)
• Mac mini (Early 2009 or newer)
• Mac Pro (Early 2008 or newer)
• Xserve (Early 2009)

You’ll need to be running Snow Leopard (OS X 10.6.8) or later.

Worth spending a few minutes on the upgrade page. Apple does a good job walking through the requirements for various Yosemite features, such as Handoff, Instant Hotspot, and making phone calls from your Mac.