After two years since owning my first DSLR, I am slowly realizing the mistakes (the simple ones) that I made while making my purchase.
I hope the following notes will help you keep away from making the same mistakes.
When I was making my purchase of a DSLR, I was least worried about memory cards. I just went with whatever card the seller gave me. My only consideration at that point in time was the storage capacity of the card.
I regret that now. Because I completely overlooked the speed aspect.