WoWDB

You will need to bring your own strong alcohol with you when you do this - Undercity is a 'dry' city. It takes five to six drinks of an alcoholic beverage with the words "strong alcohol" in its tooltip.

IMPORTANT: YOU MUST DO STEPS 5 THROUGH 8 IN ORDER. Also, you'll have to wait for Jeremiah to respawn if he's dead.

1. Buy one of the perfumes from Lovely Merchant for 1 x  Love Token.
2. Buy  Handful of Rose Petals for 2 x  Love Token or trade with another player for the petals. ( Bouquet of Ebon Roses and  Bouquet of Red Roses will also work.)
3. Travel to Undercity. Mage portal, zeppelin, hearthstone, etc.
4. Find Jeremiah Payson. He's in the central room where the UC bankers are located, on the floor and tucked back against the underside of the steps. There are cockroaches around him. If you can't find him, use (without quotation marks) "/targetexact jeremiah payson".
5. Drink the alcohol until you see a game message in your chat window stating that you are completely smashed. Pro-tip: Use the command (without quotation marks) "/console ffxGlow 0" - that's a zero, by the way. It won't keep you from slurring your speech or remove impaired steering, but it does make the blurry screen effect disappear. To re-enable, just use "/console ffxGlow 1".
6. Use the perfume.
7. Target Jeremiah Payson and throw the rose petals on him.
8. Kiss him using the command "/kiss".
9. (Regret doing this in the morning.)