pan and setting it alight. It might sound a little daunting, but it is fairly easy (just make sure you have nothing flammable near the pan like a tea towel!). Plus it's great entertainment if you have guests over.
To flambé the sauce first increase the heat under the pan to high and, standing back with outstretched arms, tilt the pan away from you. Pour in the alcohol and use a long match or lighter to set the alcohol alight. Swill the pan a few times and the flame will die down and disappear as the alcohol burns out. Always measure out the alcohol into a glass before adding it rather than pouring it straight from the bottle.
If you are using a gas stove/hob with a flame, then you can also tilt the pan into the flame after adding the spirit to catch the alcohol alight, although this is a lot trickier to perfect (and you want to make sure you don't pour the alcoholic liquid directly into the flame).
If flambéing sounds too much for you then you'll be happy to know that this step is totally optional. If you would prefer to avoid this then you can simply cook the sauce after adding the alcohol for 2-3 minutes, letting the alcohol bubble down.