How far back should I stand?

Far enough that opening the door does not put the person immediately in front of you. It reads as unhurried and it costs nothing.

A normal one, yes. A performed one is visible and works against you, because it reads as sales technique at exactly the moment the person is deciding whether this is a sales call.

What is the worst opening line?

Any question that makes the person feel they have committed to a conversation by answering it. That is the thing they are guarding against.

The first seven seconds at a door

The homeowner decides whether you are a problem before you finish your first sentence, and they are not evaluating your offer because they do not know what it is yet. They are deciding whether this can be ended quickly. Standing back from the door, being specific about why you are on this street, and asking one easy question all buy you the next thirty seconds.

What they are deciding is not what you are selling

Reps prepare for a conversation about their product and open into a conversation about whether the person is safe and whether this will take long. Answering the second question is what earns the first.

Almost everything that reads as a technique here is really about lowering perceived threat and perceived duration.

Position and posture

Standing slightly back from the door rather than directly in front of it gives the person room and reads as unhurried. It costs nothing and it changes how the first two seconds land.

Anything that signals you intend to be there a while works against you, because length is the thing they are most worried about.

Specificity beats warmth

Manufactured friendliness is transparent at a doorstep, where the other person is already suspicious. A specific, true reason for being on this particular street does more than any amount of enthusiasm.

If your opening line would work identically on any street in the country, it is telling the homeowner that you are working from a script and that ending this costs them nothing.

Common questions

How far back should I stand?: Far enough that opening the door does not put the person immediately in front of you. It reads as unhurried and it costs nothing.
Should I smile?: A normal one, yes. A performed one is visible and works against you, because it reads as sales technique at exactly the moment the person is deciding whether this is a sales call.
What is the worst opening line?: Any question that makes the person feel they have committed to a conversation by answering it. That is the thing they are guarding against.

More on door knocking

The craft of working a door: approach, first line, reading the house, what to do when nobody answers.

All of door knocking