The event will take place on February 14th at noon eastern, and there are no restrictions with regard to character race, class, or sex (opposing faction nuptials are a no-no, however). Trion is also offering up an exclusive Valentine's Day character title (Tier of Knots) to each wedded character.
RIFT's marriage mechanics will go live in the 1.7 update in early February, and they include rings, a wedding planner book, and wedding instances that support up to 200 friends. More info is available on the RIFT forums.
[Source: Trion press release]