In that case you just have to monitor the temperature. You won't be able to kill the laptop outright by overheating nowadays because processors have thermal protection circuits that will trottle back the processor or shut it off outright if it gets too hot. Use utilities like speedfan, everest or coretemp to monitor the temperature while overclocking. Keep in mind that 65-80C is common even for laptop processors running at stock, if even before overclocking you're already wandering into the 70s region, I suggest you forget it. If you can overclock while keeping temps in the low 70s or lower, then go ahead. I'm saying all this assuming you have no way of changing the processor voltage.

For those overclockers that may be frying me for suggesting such a temp, know this-laptop processors run at a lower voltage than desktop processors and hence have a much longer lifespan at the same temp. Nothing shortens processor lifespan as much as voltage.

Same thing applies to graphic card overclocking, it might or might not be possible to monitor GPU temp though, which will make things tricker in avoiding overheating.