'Do simple techniques exist that make a decent performance more likely?'

Join a regular choral group.

Warm up with a few exercises.
Don't push, let the mic do the work.
Don't growl.
Pick the key to suit your voice.
Start off with a song in an easy range.
Drink lots of warm water.
Avoid caffeine, chocolate and alcohol.
Listen to yourself.
Listen to your accompaniment. Its purpose is to keep you in tune.

'90% of intonation is attention.'

Last Saturday I listened to a Scottish woman sing Scottish traditional music. She played a huge guitar too loudly and put a microphone right at the soundhole. Result - she drowned herself out. She strummed non-stop while speaking. (Later, friends told me that they didn't understand one word she said or sang.) She sang half-a-dozen songs, all but one of them slow, slow, slow. Most of them were about Bonnie Prince Charlie or a similar disaster. I thought she would never be done.