Learn this in the order it actually matters

Who exactly is going to pay, and why now?

Everything downstream depends on this and almost everyone writes it too wide. Narrow the buyer until you could find a hundred of them this week, then name the thing that makes them act this quarter rather than next year. A route to a buyer you cannot describe is not a strategy.

Does winning another customer make us richer or poorer?

Four numbers: what a customer costs to win, what one is worth, how the two compare, and how long your money is tied up before it comes back. Work them out honestly, including the cost of your own time, before you spend anything on growth.

How big is this, in a way somebody can check?

Count the buyers who exist, multiply by a price you actually charge, then say honestly which share you can serve and which you could win. A smaller number you can source beats a huge one you cannot.

How much do we need, when do we start, and what does it cost us?

Work backwards from the end of your runway rather than forwards from today, because raising takes longer than anyone plans for. Then look at what the round does to your ownership, including the part of it the option pool takes.

Will the numbers hold when somebody checks them?

This is where rounds are actually lost, and rarely for having small numbers. Know what will be checked, have the file ready before it is asked for, and volunteer the awkward parts yourself. A founder who already knew the weak spot is trusted with everything else.