Often a picture is worth a thousand words. With that I'll show you what thin blue smoke looks like (it's ALLLLLMOST invisible). Really. White smoke; bad. Billowy smoke; bad. Blackish smoke; horrendous bad. Most instructions on most smokers frankly are wrong.
Here's a pic or two:
Seriously, the temps on the smoker (surface temp) was right at 250. The wood used in these pics was hickory. Good smokin' smoke is thin and has a light blue hue to it.
An old example pic of bad and good. Bad on the left (produced by using wet wood), good on the right. The wood applied to the fire was already warmed and dry. This is right before it got very thin, but it's still that light blueish hue: