Continuing my default DSLR camera settings series, in the above shot you can see the settings that I set my Nikon to as soon as I step indoors anywhere. I am often asked by people, what settings should I use for such and such a situation, and it is always hard to tell them because slight variations in light, subject, etc. can have a big effect. However, in my experience I pretty much always use these settings along with my external flash on my DSLR in any indoor shooting environment:
shutter speed: 1/60th
For the settings on your hotshoe mounted external flash, most of the time I find a manual power setting of 1/4th is good for lighting the intended subject and allowing the speedlight to recycle fast enough for successive shots.
As you can see the first shot was in a dark ballroom, and this shot is in a fairly well lit office, yet I used the same settings. These default indoor settings with an external flash will not light up a large room, but will still expose the subject well (the dancers) and if the room does have good lighting and is not too large, the default indoor settings can light up both the subjects and the background.
So the next time you are shooting indoors, give these settings a try and you should be very happy with the results!