UESP Forums

Hi .. When Serena is a follower I don't see an option for you to command her to do things such as pick up items? I was going to use her to load up on treasures. ??

I think this is a glitch.
For the PS3 version, you can try:

Hold down the dialogue button (Circle Button) - Serana should ask 'what can I do for you?' and follower options such as 'wait here' or 'steal this' should come up.

http://www.uesp.net/wiki/Skyrim:Serana

Unlike other followers, the option "I need you to do something." does not appear while conversing with her as a follower. You will need to press and hold E () or A () in order to issue commands to pick up, sleep, attack, etc.