Taking out stress on inanimate objects is a classic indication of stress building to unconstructive levels. Watch for signs such as slamming down a phone at work, thumping a steering wheel or slapping a wall or your own leg.
If you find yourself muttering (or even yelling) to yourself about other drivers while in the car, say, or criticising them to fellow passengers, you are creating a toxic atmosphere that can lead to rash decisions. The same goes for colleagues at work.
A supermarket-queue classic: someone has pushed in or is taking an age, and you start shifting from foot to foot, jittering your hands and muttering. All these reactions will do is perpetuate stress rather than dissipate it.
Stress is the root of almost all anger, and a bad commute exacerbates this for many people. Watch for building irritation with train or tube passengers who make too much noise or encroach on your personal space. Be aware that it is a danger sign and take steps to separate this bad experience from the working day ahead, or from dinner with your partner. Sit on a bench, or take the dog out for a walk.
Drinking tea and coffee
Stress makes you tired. Many people react by drinking endless tea and coffee; if you find yourself drinking significantly more than usual, or feel as if you urgently need to eat chocolate to boost energy levels, simply to keep yourself going, it's counterproductive. Caffeine and sugar make tiredness and stress worse once the boost wears off.
Other people's reactions
Be aware of anyone behaving abnormally around you. They often see you more clearly than you see yourself. Workmates will avoid someone angry. Children will often exploit anger and wind up a parent simply because they can. Irritating though any answering back or food throwing may be, don't ignore these signs.
Someone stressed and angry will make small mistakes, drop the ball, lose things and so on. If you find yourself making an unusual number of little errors, either at work or at home, even such small things as burning food, be aware that this is a danger sign.
Be very wary of overreaction. If someone makes a mistake and your response is instantly overdramatic ("We'll lose the client!"; "We'll never catch the plane!") take steps to try to relax.
Blame and shame
When your instant reaction to a problem is not to try to solve the problem but to look for someone to blame, you are in an irrational and pressured state of mind that is very conducive to anger.
"I can't handle this!"
The ultimate cause of stress is feeling unable to cope. If you think you can't handle a problem and this is equally applicable to a child's demands on your time as it is to a work problem, you are ripe for the spiral of stress that leads to anger.
I think about 7/10 apply to me there. You?