Are you talking about tech-wise as opposed to upsmashing, or application-wise as in setting it up?
I would assume tech wise, and it's a good idea to move with your fingers more relaxed than tense. Once you combo with relaxed fingers, it's easier to move the control stick half way up, and press A, because you're not thinking "OMG UP!!!" and jamming up on the control stick.
As far as application, do a utilt when uair juggling puts them too low to follow with another uair, or if they're gonna shffl something into you like a sex kick.