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.
2. next, is a yearning for the deen.
that is a love for Allah and his Rasool (saws), for practicing and promoting islam, you can establish this by asking them questions about hijrah or jihad, a true believer who has entered into islam wholeheartedly will yearn for such things, others will panic and run a mile at such suggestions only wanting a comfortable life here in the uk as they do not want to make sacrifices for Allah.
this is because to me and in my advice to others i tell them it is better to have a sister who practices as best she can, but maybe even new to practicing but has this yearning for the deen than a sister who covers fully, reads Quran daily but doesnt ever want to go further than this, the first sister you can help bring her up in knowledge, the 2nd is harder and most likely as you develop in the deen you might end up having to leave her behind.
3. good character
does she have good character, if not entirely then what are the flaws and can you realistically live with them? dont think you can change these, yes it might be possible but it isnt always so if you cant live with them explain you think your characters are not compatable and walk away.
4. everything else.
according to your own desires for a wife with beauty, intelligence, etc etc.