If'n yer scrrd, go to church.
Luckily fruit flies are not scary. They like sweets and moisture. And rotting fruit of course. Make sure there's no standing water in your grow area, and if you use molasses, I'd wipe out any catch trays that might have sugar residue in them, and definitely go into the kitchen and do some spring cleanin'... I find they like to live UNDER the can liner in my kitchen rubbish. That's where I've found their filthy larvae. A good shot of pyrethrin before you put the bag back in helps too!