How can I get my scratch cakes to have that moistness that you get with box cake?
Try baking at a lower temp. I bake most of my cakes at 300 degrees, with the exception of my chocolate cake which cooks at 275 degrees. I also use the heating core for all cakes 10" and over.
Moist is something you have to look for when trying new cake recipes. You're going to make alot of cakes until you find the ones you like and you can always give them to your family or friends, they will be brutally honest in what they think about them.
Good luck! HTH 
Edited to add: I found that I really like cake recipes in Collette Peters books. I am working my way through my different cake decorating books and making notes about what I like and don't like about them.
i find that a lower temp (get an oven thermometer - my oven was waaaaay out), tenting the cake with foil in the oven to stop the top crusting and also using heating cores to reduce the cooking time on 10inch cakes and bigger all help. also soak with sugar syrup (equal water and sugar boiled for a minute and add lemon or vanilla, etc) and brush on the cake before filling and crumb coating. all of these together is what i do!!
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