I haven't done it and certainly don't plan to; but if I were selecting one I'd look for the following:
Family medical history for diseases/conditions/anomalies associated with genetics. If they test the man, himself, for genetic "issues", I'd want there to be nothing that would be considered generally rare but associated with genes. In other words, I'd want to screen for potentially devastating diseases/conditions.
I'd want to rule out a family history with schizophrenia or mental health problems known to be linked to heredity.
Since the father wouldn't be around, I'd probably aim to find someone of the same race as I am, only because it would make things simpler if the child and I were of the same race. (Why have to answer questions or have some "we're different-colors" issue when you don't have to?
To be honest, I'd want to screen out anything like an outrageously unattractive nose or horribly receding chin. I wouldn't look for movie-star looks - but just nothing that was likely to make the child feel he needed plastic surgery to correct it (the extreme stuff).
I wouldn't give "two hoots" about IQ (and I think women who seek out Nobel-Prize types, and pay extra money for it, are silly). As an adoptive mother and biological mother, I am convinced that it is primarily nurturing from birth that determines the development of a child's brain. Those women who look for Nobel-prize types as sperm donors usually are so focused on intelligence and education that they nurture the child in a way that is almost certain to result in an intelligent child (and then the mothers believe it was their selection of a donor that caused the child to be intelligent).
So, that's about all I'd screen for.