Negotiation first, because the LOI is a negotiation that owners mistake for paperwork. Then the specific mechanisms that move money quietly: earnouts, deal points, and the vocabulary that lets you read what you are being handed.
The foundation. Interests rather than positions, and why your walk-away option is the whole game.
The counterweight, from a practitioner who thinks principled negotiation is too tidy.
What earnouts actually do to the parties, from the research rather than the pitch.
Why the structure exists at all, and the evidence that audited books buy you better terms.
What terms are actually market in private deals, which is the only real answer to "is this normal".
Keep it open while you read the documents. Free, and it removes the vocabulary disadvantage.
You will read an LOI and see what it has already conceded, and you will know which three points are worth spending your negotiating capital on.