I can't be sure what didn't look right but a fun thing to experiment with on the D70 is to try changing the flash sync mode to 'rear curtain'. It causes the strobe to fire at the end of the exposure instead of the beginning... useful with slower shutter speeds by allowing the shadows to fill in with ambient light and then freezeing the subject with the keylight. I'm pretty sure you're manual camera guy so you can ignore the 'slow' sync mode which does something similar but in auto-exposure modes.
You may already know this part... The formula for mixing light is simple.
Aperture controls the flash exposure, shutter speed controls the ambient light exposure. It's the same principle as for manual fill-flash. Play with it, look it up, play with it some more and it'll come to you. Just remember that formula... books will obfuscate the hell out of it; when things look really complicated, go back to the formula.
Admittedly these aren't great shots but they ARE good examples:
Rear curtain sync to get the candles and christmas lights...
D1X 28-70mm f13 / .5s
Rear curtain but I accidentally moved the camera during the exposure...

D1X 28-70mm f19 / 1s
...kinda weird if you look at it a minute.
Enjoy,
Chip