Currently whenever I write a query that is adding columns that can contain nulls I resort to wrapping each field in
coalesce, such as
coalesce(score1,0) + coalesce(score2,0).
Is there a better way to handle this, or is this the standard practice?
That's pretty much what you have to do. Since NULL + anything else is NULL, you have to wrap each column in its own isnull(), coalesce() or CASE.