Keep it quiet.
When dealing with a sales person, deflect any/all inquiries as to how you are going to pay for the vehicle. If they press you just tell them that you haven't decided how you are going to pay for it and then insist on discussing the vehicle's "drive out" price ONLY. You need to negotiate the bottom line "drive-out" price because many/most dealers are tacking-on exorbitantly high documentary (and other) fees to the vehicle's sales price. Many states (like Texas) do not allow buyers to opt-out of these fees, so you need to negotiate the bottom line "drive out" price including all of the fees from the get-go.
The absolute WORST thing that you can do during negotiations is to let them get you off of the price and onto the payments. If you have done your homework and legwork before you started (like all of the experts tell you to do), you should already have your financing arranged and know how much you can afford to spend to get to your payments. You can't purchase a $40k vehicle for the payments of a $30k vehicle, the math simply doesn't work. The three ways that they get there are by balloon payment financing, a lease, or extending the loan term to... forever. You can't blame the dealer for doing this, they are in business to make money, as much money as they can on each transaction, you can only blame yourself for falling for it thinking that you are getting something for nothing.