As you train and practice with your dog, keep "environment" on your radar. Selecting the correct environment for your dogs work is very important. Ultimately most dogs can do well and thrive in most environments, but during early and middle training the environment will have an effect on how successful your dog is, and smart trainers incorporate different environments into different lessons so that the dog improves.
Environments vary on how familiar they are and what level of types and distractions there are. Some dogs are even affected by the weather! Although real-world training in different environments, here an idealized progression of environments for you to practice with your dog.
1) Your basic "home" training environment is usually your living room or kitchen. This is the easiest of the environments; there are no distractions and the dog is completely familiar with and calm in the space.
1-b) Still your own home, but different rooms in your home, possibly ones where your dog does not go often, such as the garage or a child's bedroom. The level of difficulty is still not high.
1-c) The backyard, balcony or deck of your home. Not too many distractions other than just being outdoors (so maybe mild scent distractions carried in on the wind, or a spot where a squirrel has been), but some dogs are used to playing in the backyard and may have difficulty transitioning to work.
1-d) The front porch and front yard of your home. Still your home, still familiar, but now there are going to be distractions popping up. Neighbors walking by? Neighbors walking by with dogs? Traffic and bikes?
2) Low-distraction familiar areas. I use empty parking lots or sometimes basketball courts for this.
3) Medium to high distraction but familiar areas. For me this is my local park. (Trenton Park, if you really want to know. It's a tiny park in North Portland.) Depending on the day, there are usually medium-level distractions (other people and dogs) and sometimes high-level distractions (off-leash dogs playing fetch, kids, flocks of birds, squirrels.)
4) Low-distraction novel areas. These look a lot like #2 above, but they are "novel." That means the dog has never been there before.
5) Medium to high distraction novel areas. Again, the distraction level is medium to high, but add to that the "novel" factor -- the dog has never been there before. For my medium-distraction novel areas, I like to work on NE Alberta, N Mississippi, Hawthorne, or the downtown part of St. Johns. For the high-distraction novel areas, nobody's training adventures are complete until you've attempted the downtown Portland waterfront!
What do you practice where?
Home training (#1) is where you introduce all new commands and work through all the steps to getting them solid and reliable. The dog should be fluent in the home steps 1-1c before you attempt to bring them anywhere else! Home training is also where you return if you are not having success at a higher level or if you realize that your dog doesn't actually understand as much as you thought it did.
After that, you can work through the levels in order. Keep your eye out always for good potential novel environments! When you go to the novel environments, it's best to plan to concentrate solely on working your dog until it is extremely good at novel environments. So don't expect to sit down at a cafe on NW 23rd Ave and have your dog do a perfect settle, if you have never been there and your dog is not yet fluent in novel environments.
Treats and weaning off treats is also something to keep your mind on when you are working on environments. Treats should become more frequent, the more difficult the environment. A "sit" which at home just earns praise should earn a treat in a highly distracting environment, because it's harder. (Also because it has the benefit of conditioning the dog to actually pay more attention to you, not less, in the face of heavy distractions.)
Most dogs require multiple practices at multiple novel locations before they are "fluent" in any location. Once it has achieved fluency, the treats can decrease and stop. But not until then!
Let me know if you want any help figuring out your training environments or if your dog is ready to advance a level, or if you are totally stuck in a specific environment!