when do you take THE SEED PODS off the plant

Not till I'm ready to plant the seeds... If then.

Very good idea to leave those pods alone... Many plants attract song birds!

What do you plan to do with the seeds? If you plan to keep them to grow more plants, then let them ripen and dry on the plant. Some plants you have to watch closely so the seeds don't disperse before you get there. I usually let the first ones open so I can better judge when to harvest the rest.

If you are trying to keep a plant from going to seed, deadhead the old flowers before they get to seed stage. That will encourage more flowers and save the plant the energy it would use in production of seeds.

The longer you can leave them on the plant, the more likely they will be fully ripe when you collect them. Depending on the plant, the seed pod is likely to turn brown and look dead or start to crack open when the seeds are ripe.

The main reason not to leave them on the plant right into winter is that the pods are likely to open enough to let the seeds fall out. (And they might get rained on, and rot. Or birds might eat them so you can't save them.)

The type of plant REALLY matters since some plants hold their seeds for weeks, and others ripen and then "pop" overnight.

If they are like poppies, you might need to "bag" the pods before they turn brown, to be sure they don't ripen sneakily, then open and drop overnight. Often people use "organza bags" from a craft store bridal isle to catch the escaping seeds and trap them in a drawstring fine-mesh bag that lets air and rain pass through.

It really depends on what plant you are saving seed from.