First you need to get prepared: a dremel with a cut off disc or rotory saw attachment works great and causes little trauma. If lacking this then a good pair of side cutters will have to do. a bowl of tank water big enough to place the frogspawn in after the cutting for rinsing off.
Before you take it out of the water, you want the polyps to retrack, wave you hand making a little wave near the polyps to make them retract. Once they are in you can take it out and look for a good spot. Some where at the bottom of the branch is where you want to cut. AT the "V". This is where the dremel comes in handy.
hth
