If you have not been kissed before in Paris, here are a few places where it might happen according to Ou s'embrasser a Paris (Where to kiss in Paris, in French only) by Laurianne Barbier (Rédaction Voyages-sncf.com).
She starts with Fontaine Medicis in Jardin du Luxembourg.
She then offers a number of other sites including lesser known Musee et Jardin Albert Khan in Boulogne-Billancourt with its multiple gardens (English garden, Japanese garden, French garden) and mini forests (Blue forest, Golden forest, Foret Vosgiennes) and Butte Bergeyre (19eme arrondissement).
If your lover or better half does not like climbing steep hills, don't take them to Butte Bergeyre (pictured above).
Besides romantic advice, SNCF is also currently having 2 for 1 offer, Offre Duo (French page) for Spring travel on TGV and Intercites trains to and from Paris, Marseille, Brest, Clermont Ferrand, Toulouse, Bourges.
Book your trip by April 23 for travel between April 12 and May 13, 2013.
In France They Kiss on Main Street
(Photo of Butte Bergeyre from Butte Bergeyre piece on Peter's Paris– June 9, 2010)