The order things happen in
A proposal is made, usually between families. The families vet each other. The candidates meet, with a mahram present. Conditions and mahr are agreed. The contract is made with witnesses. The walimah follows.
Almost every problem comes from doing these out of order, most often the candidates becoming attached before the families have vetted anything.
The meeting
A meeting with a mahram present is permitted and encouraged. Looking at the person you intend to marry is explicitly permitted.
What is not permitted is an extended private relationship in the name of getting to know each other. That is the thing the whole structure exists to prevent.
The contract
The essentials are the offer and acceptance, her consent, the wali, two witnesses and the mahr. Everything else is custom, and custom varies enormously by region.
Conditions are attached to the contract itself. This is the moment to have them written, not the week before the walimah.
Where time is lost
Long engagements. Every additional month between agreement and nikah increases the chance of it collapsing and of something impermissible happening.
Waiting on a walimah budget. The walimah is a sunnah and it is meant to be simple. Delaying the nikah for a hall is the wrong way round.
General guidance, not a fatwa. Where something is disputed among the scholars we have said so, and you should ask someone you actually learn from rather than relying on a website, including this one.