I've only done very little patch clamping, but I do have experience in general with similar preparations in my year of teaching a neurophysiology lab (which I was woefully unqualified for 😛). The biggest things that come to mind are to make sure you're using a proper solution to store the sample and don't stretch/bend/poke/suck it too quickly/hard. Both of these things will kill it and you won't get any results. If you need to stretch it, doing so slowly will decrease the stress. If it gets dried out, too dilute/salty, or the correct ions are not present in the correct concentrations, the characteristics will change and it may die.
Other than that, it really depends on exactly what you're doing and what sort of sample you're using. Just be patient and keep breathing.
