Internal reference - copy or link?

Question

Pretty often my answer refers to other answers on this site, like:

1. Do this, as described in that question
2. Do something else
3. Consider using this answer for finish.

You know, step-by-step solutions where some steps was already evaluated.

Should I:

• Link to original question & answer, so users who know how to do it don't need to scroll and users who don't know can click and read? This way, if there will ever be a better solution for specific step, reader of my answer will get it, too.
• Copy a part of original answer into my own, and leave "taken from" link? This way if original question will get deleted my answer will still be complete, but on the other hand it may get outdated if original one will get updated or will get proven or rendered false by future events.

What's the proper way?

To make it bold - this is not about external links.

Answer 1

What I would do is:

• Write my answer tailoring it for the question I am answering
• Link the other answer, especially if I used it as guide to answer

If the answer is too long, and I don't want to repeat what already said, I would:

• Make a summary of what reported in the other answer, giving the most important points/information
• Link to the other answer for a more detailed explanation

Also in this case, I would tailor the answer for the question being asked. For example, if the terms used in the other answer don't match the current question, I would guide the OP translating the terms used in the other answer with terms that apply to his question.

Before answering, I would be sure the questions are not duplicates. If there are not significative differences between the answers, I would vote to close the most recent as duplicate of the other one.