Since the Raspberry Pi 2 Model B looks a lot like the Raspberry Pi Model B+ you'll want to get good at identifying which you have.

PCB Silkscreen Name

First up, you can look for the name which is near the GPIO connector:

Look for the "Raspberry Pi 2" text and you're golden!

Broadcom Logo on Processor

Since the Pi 2 does not use 'package-on-package', assembling the RAM on top of the processor, you can easily spot the Broadcom logo on top of the quad processor

If you don't see the logo, or you see something like "Samsung" or "Hynix" it's a B+

RAM chip on bottom

The Pi 2 has a RAM chip that is soldered onto the bottom of the Raspberry Pi's circuit board. The B+ does not have one at all, the RAM chip is soldered directly on the processor. So just look for a black square chip on the bottom of the PCB. The naming and logo on the RAM may vary depending on what company supplied the memory.