depends on how much money you have to spend and how much storage you want, do you want a ssd (fast but expensive per GB of storage.) or a normal hd (slower but lots cheaper per GB of storage.)
as for physical dimensions you want a 2.5inch drive maximum of 9.5mm in depth.
hd :- http://www.newegg.co...ING&PageSize=30
ssd :- http://www.newegg.co...08120 600038463
as for memory i suggest visiting the crucial site :- http://www.crucial.c...en/apple-memory
answer the questions and they will list compatible memory for your model of mac.
curious but why do you think you need both new memory and hard drive? nothing wrong with that, it's just usually people only need 1 or the other, more memory or a new hard drive because old has failed, and why i'm curious.