How to guarantee rows order
ORDER BY is the only way to guarantee order. If you have a unique key (primary key, unique index) then order by this, otherwise you'll need to order by all the columns in the table. If you have multiple unique keys and one of them is the clustering key for the table (or the first part of a larger clustering key) then ordering by that would be most efficient. As you don't know ahead of time what table definitions you have you will need to work out what candidate sorting keys you have by checking the contents of sys.indexes and friends.