Most of the table service restaurants in Disney parks & at resorts take 1 TS credit per person. Some of the restaurants do not take the dining plan at all (Rainforest Cafe outside AK & in DTD, and some of the DTD restaurants do not take dining plan.
Signature restaurants and the dinner shows are 2 TS credits per person so if both of you go to a 2 TS place they will take off 4 TS credits. This list from the
DDP sticky at the top of the dining plan board includes these places:
Signature restaurants requiring 2TS credits per person:
Artist Point (Wilderness Lodge)
California Grill (Contemporary Resort)
Cinderellas Royal Table character breakfast/lunch/dinner with photo package (Magic Kingdom)
Citricos (Grand Floridian)
Flying Fish Café (Boardwalk Inn & Villas)
Hollywood Brown Derby (MGM Studios)
Jiko - The Cooking Place (Animal Kingdom Lodge)
Narcoossee's (Grand Floridian)
Yachtsman Steakhouse (Yacht Club)
Dinner Shows requiring 2 TS credits per person:
Disney's Spirit of Aloha Dinner Show (Polynesian)
Hoop-Dee-Doo Musical Revue (Fort Wilderness)
Mickey's Backyard Barbeque (Fort Wilderness)
That thread has loads of good info on it -- you might want to take a look
http://disboards.com/showthread.php?t=2054845