[quote name='stingrayPete1977' timestamp='1486992235' post='3236058']
I'd say even taking a clip on tuner out of the house is amateurish, looks like you've had it for Christmas with the guitar you're playing to me. I wouldn't tell anyone they shouldn't though, it's up to them.
[/quote]
Nowadays clip-on tuners are more accurate than a pedal. Plus you can't inadvertently leave yourself muted after tuning up.
The most important thing is to be prepared.
Have all the skills necessary, don't try and con your way through something. A band I regularly play for had a dep, he said he could read and improvise from chord charts, turned out he couldn't.
Stupid things too, like remember to take your glasses, music stand, music stand light, spare batteries, a spare cable. Have the correct tools for the gig.