Should I tell the dealer I have a trade-in right away?

There's no single rule, but many shoppers find it clearer to agree on the vehicle price first and then introduce the trade-in. That keeps the two numbers separate and easier to compare. Either way, get the out-the-door price, the trade-in value, and the loan payoff written down individually. Having outside offers in hand, such as instant online quotes, gives you a benchmark if the dealer's trade offer seems low.