Good looks and service at a fair price, on time, clean, well dressed, amiable, at least acts like they are really into me and our session, etc.

Granted a newbie provider might have some rough edges to hone down, but that could be off-set by some innocence, which can be charming in and of itself.

I would add it's important that she understand discretion and is discreet. That may sound redundant but people don't always put the two together