How can I insulate my thermistor?
I have had many problems with my heat shrink for the thermostat on my Anet A8 melting from the heat block.
Is there a way I can insulate my wires from heat but still have enough room to put the thermistor into the block?
For an illustration of how to employ the Kapton tape, that is mentioned in the answers from Harvey Lim and Howler, watch How to build a RepRap Prusa i3 (Assembly 7) at 21:30:
From 15:10 the heater and thermistor is connected up, you may find this also useful. Note that, at 20:45, the heatshrink is only used over the soldered connection, and not all the way up to the heatblock:
Also, more pertinent to your printer, from Anet A8 Review – Best cheap 3D Printer?, see that the thermistor wires are also wrapped in Kapton tape in this photo:
Note that the Kapton tape is wrapped around the wires, almost right up to the thermistor, and will be touching the heating block, when the thermistor is inserted into the hole - there is no problem of it melting, due to its high melting point.