Which fundamental questions about our future life must be settled before the shidduch, and which can wait until marriage?

People have very different ideas of marriage, so he advises asking specifically rather than in general terms. How should a disagreement between husband and wife be resolved properly; on what would you never compromise in choosing a spouse; what would you do if I lost my job and took it hard; watch the game or learn Gemara with your son before his test; must a wife follow all her husband's minhagim; what does your ideal marriage look like; a shiur or the parent-teacher meeting; may a wife have an opinion about her husband's clothes; are separate vacations with friends acceptable; what do you expect of me as a spouse; do you accept physical punishment of a child.

“Different people have different ideas of what marriage is and how they plan on raising their families”

She looks at it from the side of the person proposing the shidduch: some things are so obvious that people forget to ask about them, and for the other side they turn out to be deal-breakers. Her list: do they plan to live in Israel, or definitely cannot; must they stay in their city to finish studies or be near family; if the goal is kollel, for how many years, do both of them and both sets of parents agree, and does everyone understand kollel life the same way; does the family insist on marrying only within its own kind; does the person drive; does yichus (family lineage) matter; is the proposed man a kohen.

“A Shadchan needs to know if there are any circumstances that would absolutely prevent a shidduch from succeeding”

She examines the disagreements that surface during the process and cannot be laughed off: you believe finances are the couple's business alone, and he happily tells you that his parents manage his accounts and will go on helping with the hard money decisions; you dream of your own Shabbos meals, and he wants every Shabbos at his parents'; you want to send the children to your favourite camp, and he only to the family one; you plan the children's schedule with colour-coded charts, and his philosophy of parenting is that nobody set anything on fire today, so all is well. Things like these can make you doubt the prospects, and sometimes you will indeed decide not to continue. But if the relationship as a whole is good and moving in the right direction, even a tricky conflict does not need to be a reason to say no, provided you can talk about it.

“even a tricky conflict doesn't need to be a reason to say no.”

They divide it by time. The big things, the style of davening, family customs, halachic preferences, form the backbone of the home, and these are looked at from the very start of considering a shidduch. After the wedding the second part of the work begins: attention to all the small, less obviously spiritual expressions of your spouse's soul, chicken instead of meat, blue instead of purple. The specifics themselves do not matter; what matters is how you handle them.

“The exact preference is not important, the implementation of the preference is.”