Compared to the era where photos were originally shot on film, nowadays most cameras use a new type of media, flash memory to store hundreds/thousands of photos. These "Flash memory" include the most frequently used SD/SDHC/SDXC cards (secure digital) majority of digital cameras use this type of storage, along with Compact Flash which is the older ancestor still being used in the higher professional Dslr cameras.
Before jumping into the scene it is important to know card speed. It actually means the speed the memory card can perform in terms such as writing into the card, and transferring. I posted the small graph below showing the various speed. There is 4 standard rating, the numbers respectively guarantee that the card will perform the minimum performance point.
Broad picture
class 2 alright for point and shoot
class 4-6 good for point shoot HD-Full HD video
classs 10+ high end point shoot/DSLR full HD video (highly recommended)
But unfortunately this table is becoming outdated, since faster capacity/speed SD cards arriving to the market (as of 2013 point). The majority are dominated by Class 10 SD cards, because there is no rating above class 10, and prominent manufactures try to differentiate themselves by writing the speed on top of them for example 30mb/sec on Sandisk Ultra SDHC and the higher ends can reach 120mb/sec (both being on same scale class 10) the speed wont affect that much on digital camera users, but heavily affect Dslr users.
For manufactures, the most dominant company selling high reliable SD cards in Japan with highest share is most notably Sandisk headquartered in the US. They provide one of the top quality SD cards around in terms cost performance, and other company worth mentioning is Transcend from Taiwan famous for memory cards. I personally use Sandisk SD cards and Transcend CF cards for my D800 since the CF coming from Sandisk seems to be really expensive. Others would be Lexar, Kingston, Toshiba, Sony, Panasonic etc. Although I am Japanese, I preferably use Sandisk, and Transcend over the Japanese manufacturers. (although the quality might be good, I cannot pay the high premium).
I cannot say which brand is the best but It seems to me that its worth investing in the mid range capacity cards rather than buying only one in the extreme high end (64-128GB SD). Before you know it the price of the higher end will drop drastically thus be waste of money. I currently use a 16GB-32GB range SD/CF which is around 20-30USD compared to 60-70$. I believe its Quantity>Quality since you never know when One will fail so instead of having one 32GB SD its wiser to have 2 16GB SD so you can keep shooting if one fails.
