It is best to use flower stems that have at least half of the flowers left in good condition. The best results are obtained when the bracts covering the nodes are fresh, and not dried and brown. After removing the stem, gently clean the entire stem using a soft baby’s toothbrush, and antibacterial hand soap, wiping from the bottom of the stem towards the top of the stem.  Without rinsing off the soap residue, immerse the stem in a 10% bleach solution for 1/2 hour.  During this time I use a hobby style light/magnifying glass and a pair of eyebrow tweezers to carefully remove the bract from around the node after it has been ‘ringed’ with a sharp blade.  Care must be taken to remove all traces of the bract, and it doesn’t seem to matter if a portion of the “bark” of the stem has to be removed, as long as the entire bract is removed. I work over a container of the bleach solution, and often re-dip the stem and tools into the solution during removal of the bract. The next step is to cut through the stem 30mm below the node, and 20mm above the node with a fresh single edged razor blade. The cut above the node is at right angles to the stem, the cut below the node is on a long angle to expose as much of the stem as possible which will contact the medium. The sectioned pieces of stem are placed into the plastic containers that 35mm film comes in. The containers are filled with 3% Hydrogen Peroxide, a tiny bit of the soap, and the lids are put on. The sectioned stems are left in the Hydrogen Peroxide for up to 2 hours, shaking occasionally. The container is placed into the transfer chamber, and the stems are then removed from the Hydrogen Peroxide. With a fresh sharp single edged razor blade trim 5mm from the top and the bottom of the stem. Without rinsing the stem, place in the tube containing the medium, with the node flush with the surface of the media. While inserting the stem into the media, push the stem deep into the gel to allow the medium to thinly coat the entire node, then pull it up flush with the medium. Cap the tube and place the stem under a single fluorescent tube for 16 hrs/day. I have found that temperatures nearing 80 degrees F are optimum for kicking the nodes into development. I am currently using Phytamax Orchid Multiplication Medium P6793 from Sigma, full strength, as per the instructions.  This method reduces the time involved in rinsing the bleach solution off of the stems, and possibly introducing contamination. The bleach is neutralized by the Hydrogen Peroxide, and the Hydrogen Peroxide is neutralized by the UV of the fluorescent lights. The aggressive cleansing action of the Hydrogen Peroxide does a great job of cleaning in behind the node.  Only use fresh Hydrogen Peroxide from a recently opened bottle. Air and light degrade it rapidly.  Spraying the plant and stem 2-3 days prior to harvesting the stems with a systemic fungicide like Subdue 2E, makes a huge difference towards reducing systemic contamination.