Install an SDD in a MacBook Pro 13" / Mid 2012?

"You certainly can install an SSD in your machine, but where do you want it? You can either replace your existing hard disk with an SSD, in which case you'll want to use our hard drive guide. There is also the option of removing your optical drive, though, and replacing it with an SSD installed in an optical bay enclosure.

As for brands and models, we've been really impressed with the speed and reliability of Intel, Crucial, and OCZ solid state drives."

I agree, I just switched the original 500GB HDD by Hitachi for a Crucial BX100 500GB and it runs buttery smooth, also what's important Crucial lets you download an image file to burn onto a CD and create a bootable CD to update the firmware of the SSD without having to plug the SSD to a PC computer (most SSD manufacturers would not allow Mac OS users to update firmware via Mac OS, they only give you a handful of software options for PCs running Windows). I am super happy with mine, shall my optical drive fail I'll simply get a data doubler and pop in the original 500GB HDD for additional storage (it'll stay in the box until then). Have fun fixing!

How do you decide what size SSD to get ? Im thinking about doing this with my MacBook pro same model but have no idea what size SSD to get. Was thinking of doing a RAM upgrade too but which would be better to do first ?