My indicator is apparently my hat...if it's undisturbed, all is well. When my hand goes to the bill, it's the first warning sign...when I keep adjusting it, it's a tad worse...and if it gets snatched off, everyone takes a step back. I once went to a practice bare-headed...the team told me I HAD to wear a hat from then on out so they had some warning when to tighten up!
