Ancient Jewish secret: don't peek! Put those dumpling/matzo balls in, put on the lid, and don't you dare peek, stir, or shake. They'll come out more steamed than boiled, perfectly light and airy, and your broth with be beautiful.

Cook the dumplings in a separate pot of salted water - I love the Joy of Cooking recipe for spaetzle, perfect for chicken soup.

almost any dumpling cooked in the stew/stock will add texture to the liquid. It is inevitable. If you want to avoid it (not sure why, since I think it makes the soup even yummier) is to cook the dumplings in a separate pot of stock or liquid and then transfer them when done.

It can also depend on the consistency of the dumpling. You can make then a little dryer in the hopes that they will hold together more.

There are many ways to make something folks call dumplings. Some are supposed to resemble a steamed drop biscuit and some a wide thick noodle.

To me the ones hardest to make are the steamed drop biscuit type. I make batch of drop biscuit dough. Get the chicken and gravy mixture heated to boiling, then set the heat back to a minimal simmering level. I drop balls of dough into the gravy using a 2 ounce ice cream scoop. Then I put the lid on and cook the dumplings for 15 minutes before checking them. They should be cooked all the way through at this point. If not, I cover and cook another 5 minutes.

To me the secrets for these types of dumplings are:
1. To Not stir the pot once the dumplings have been dropped in
2. To Keep the heat high enough to just barely simmer as a roiling boil will tear them apart.
3. To have a tight fitting lid to hold in the steam which cooks the dough

Hope that thelps.