What most people do is just list all the subjects their character took OWLs and NEWTs in, and then they put the score (O, A, E, P, D, T).

Passing grades are:

O (Outstanding)
E (Exceeds Expectations)
A (Acceptable)

Failing grades are:

P (Poor)
D (Dreadful)
T (Troll)

So you would list all the subjects your character took OWLs in, and then put the grade, and then you'd list all the subjects your character took NEWTs in, and you'd list those grades, as well. Remember, though, that qualifications aren't just OWLs and NEWTs. If your character has any special skills, degrees, awards, experience, etc., those are all qualifications, too.

Here's an example of how you might answer that question:

OWL Scores
Ancient Runes: P
Arithmancy: T
Astronomy: E
Care of Magical Creatures: O
Charms: O
Defense Against the Dark Arts: O
Herbology: O
History of Magic: E
Muggle Studies: T
Potions: O
Transfiguration: E

NEWT Scores
Astronomy: E
Care of Magical Creatures: O
Charms: O
Defense Against the Dark Arts: O
Herbology: O
History of Magic: E
Potions: O
Transfiguration: E

Another thing to remember is that it's perfectly okay for your character to have a variety of scores. It's more realistic to see strengths and weaknesses, and it also helps gear your character toward a job better suited for him/her. You wouldn't report an O in Herbology, for example, if you have a character that wouldn't like to work with plants. Things like that.