How do you teach "off"?

You can teach off with still allowing access to furniture if you choose.  The value of off is the meaning of all four on the floor.  It can work for greeting jumping, counter surfing, or furniture.  The best thing to do in this situation is a drag line as well as planned training situations.  One of the most important factors is something good (to the dog) happening after the command is given and followed.  Dogs tending to be doing something enjoyable (or they wouldnt be doing it) when we use an off command.  So pets, a body rub, a cookie, a toy thrown are all considerations to follow getting "off" something.
 
Training.  Find things to jump on.  I like to have jumping on me under command, so I would use that as one activity.  I would look from some small raised option (stool, step to the house but use the side not usually used for enterance, a couple few bricks with a towel over them, etc)  Lure the puppy up to the selected option.  Then  with a collar guide,  movement from you, or a lure, entice the puppy off the option selected.  As soon as the puppy is moving OFF the option, say the command "off"  repeat up to 5 times,  switch to some other practice.  Go back and forth between activities until puppy has done off about 15 times.
 
Drag line....While under observation, attach an inexpensive leash or cord length to the buckle collar.  Let the puppy drag that around,  puppy gets on something, use the collar to remove them.  Gentle steady tension.  Wait until the puppy is actually moving off, repeat command "off"  and offer the alternate enjoyable event.  Remove line from puppy when not under supervision.

You're smooshing a lot of behaviors into Off, IMO.

I would break this down a little bit. If he's not allowed near the table, then he should just get time out every time he gets near the side table. Using Off with the side table gives him the option, which it sounds like you don't want.

Chairs and stuff he should know how to be asked off so you don't have to shove him off. But then I would ask him to do something incompatable with getting back on, like laying down on his own bed. Otherwise yes, it becomes a game.

ORIGINAL: Sue and Buddy
I thought Buddy knew what this meant, but I think he is only responding to me coming to him when he is on the couch or chair to make him get off.  Also, is it wrong to let him on the furniture, but make him get off when he is doing something innapropriate, like scratching the fabric or walking onto the side tables?  Should it be one or the other...always on or always off?  Am I confusing him? 
Sue

 
I think it's perfectly fine to tell your dog "off" the couch for inappropriate behavior.  Being on the couch is a privilege, so you're dog needs to behave when on it.  Also, if your dog really enjoys being on the couch (like mine does), being told "off" should be sufficient punishment for whatever bad behavior he was commiting.  My dog is allowed on the couch but only with permission.  She's supposed to sit and wait before being allowed to enter the living room, and again before being allowed on the couch.  If she jumps up on the couch with out being told "OK, up", she's told "off", followed by "sit", and "stay".  Then we tell her "OK, up", and she can go on the couch.  She's a puppy who was only allowed in the living room fairly recently, so she doesn't always follow the rules, but she's definitely learning.
 
Also, in response to mrv, I also incorporate "up" and "off" into a variety of scenarios... I think that for commands that are sort of general, it's best to teach the dog all the applications for which you would want the command used.  So, when she tries to jump on us or other people, she's told "off", then "sit".  After a few moments of sitting calmly, we'll then tell her "up", which means she can jump on us if she wants.  The goal is to train her to sit first when greeting people, and that she can only jump on people when given the command (we're trying this method because we have a few friends who always pat her when she jumps on them, and it kept destroying our  training to not jump on people).  I also work on "up" and "off" in the back yard, where I have her jump up and off a chair for treats.  It's really just more training for the couch scenario, but in a setting where she's a little more focused because I always have a treat ready, and the plastic chairs outside aren't that comfortable so she's not in a frenzy to jump up on them