Question
I live in Albany, GA.  I have started a potato vine from a sweet potato in my window.  It has taken off like a rocket and is now in soil.  I was told that if I want it to grow think that I need to cut it back.  My questions to your are when, where and how do I cut the vine back?  Next question is when the plant gets big enough, what do I need to do to start more plants from the vine?  Thank you in advance.

Answer
You can cut the vine anytime, as much as you want. It will just keep growing. The best place to cut it is next to where the leaf is attached to the stem above the leaf. Leave the leaf and cut away the stem. The new growth will start from the leaf node.
The stem that you cut off can be placed in a glass of water, and rooted and planted in soil to make a new plant. You will need to cut the stem just below the leaf, this time you remove the leaf, and some of the leaves if they will be below water. The roots will grow from the leaf node.

It is just that easy...