i can say what i looked for before i found my wife, who alhamdulillah fit my criteria.
1. my first was to establish whether a husband or wife is upon the correct aqeedah and manhaj, fiqh not being important on this level.
even if someone is not of the correct aqeedah and manhaj is this due to ignorance or misguidance?
i.e if a husband or wife says Allah is everywhere, meaning no where or without a place and you explain in the marriage negotiations that they are incorrect and give the daleel and they change their position and they just didnt know better themselves.
you can ask this by asking them certain questions, such as where is Allah? then having follow up questions. like 'what would you say if i told you imam abu hanifa held Allah be above his throne, would you say you are still correct or imam abu hanifa was correct in his understanding? also giving one or two of the ayats where Allah says he rose over his throne.