When taking clones you need to focus on 2 things first,
1 You are using a sharp blade/scissors,
2 All equipment being used and surrounding work area is sterile,
Ideally you are going to want to take your clones off of the bottom of the plant, This is because there is more nutrients at the bottom of the stalk.
Your cuttings need nutrients to survive until they form roots so this is why most growers cut clones from the bottom of the plant, You should also feed your plant 1-2 hours before taking your cuttings so they are able to absorb extra nutrients before being cut off the stock to survive until roots form.
When taking cuttings cut the stem of your cutting on a 45 degree angle and place into a cup of room temperature water as quickly as possible, if you dont get your cutting into water quickly enough your cutting will suck up air causing an embolism,basically the air blocks your plant from absorbing nutrients.
We reccomend beginners use Rapid Rooters for their starter cubes as they contain nutrients to feed your cutting in its first week/weeks of life, you can also use rockwool cubes or jiffy pucks however these do not contain any nutrients.