We use a regular snap-lock collar for our dogs while they are out in the yard. It has an ID tag, rabies tag, and license. When we go out for a walk, they wear training/choke collars. When they have the training collars on, they are more on their toes and know that we are not playing around. It’s like getting dressed for work.
At this point, hearing the collar jingle is enough to remind our Goldens not to go beyond the end of the leash; if they feel it tighten at all, they “check” our location and make sure they are not going to pull; they are praised for checking–“Good check, Loki.” Check is a ‘look at Mom/Dad’ command and we use it walking; if they get too far out for our comfort we have them check, reminding them of the boundary.
For just walking around without heeling, we just start out with a “Let’s go.” We really don’t need to heel our dogs too often, but we use the “heel” command when we do. We try to keep our dogs to the left both for consistency and as a safety factor–I like to know which direction the tripping is going to come from.
We have three dogs and they are let out frequently because we have a fenced yard so we don’t have to go for a walk to potty. If one of them needs to go out NOW, she’ll come find one of us and just pester us until we ask her if she needs to go out. If she does, she’ll beat feet it for the downstairs door, if not, she’ll give us further clues to figure out what she really wants. You learn to pick up your dogs’ signals from being around them.
As Lissa suggested, you can train Zoe to ring a bell or use some other signal. The only problem is that she may also use it no matter what she wants to go outside for rather than just when she needs to potty. Dogs are individuals and some dogs are better communicators than others, just like people.
As far as timely enforcement goes, first things first–get her attention on you before giving the command. Preface the command with her name to “turn on her brain”–so she knows you are talking to her. Say, “Zoe, sit.” Also use any hand signal you are trying to teach her at the same time. If she sits, reward her*, “Good sit, Zoe, what a good girl, oh you’re so smart.” If she doesn’t, put her in a sit and then reward her.
A “sit” is different than a “sit-stay” where you expect her to keep sitting for a longer period. If you want her to stay a long time, put her in a “down-stay”. “Down” is a hard command to teach some dogs because they are vunerable in that position and they don’t always like that, so don’t get discouraged if you have trouble with that one.
Also, when you notice Zoe doing something, praise her. If she’s laying down at your feet, calm and cozy, give that a name and praise her for doing it. It can be “Good down, Zoe” or “Good settle, Zoe” or whatever. Reinforcement and consistency is everything.
*I hope that you are doing a praise-based reward system rather than food treats all the time, otherwise training your dog can make her fat. 