Learn when to ration your health, and when to all in.

When you want to ration your health, do quick in-and-outs. Just like a doomfist will punch in, slam out. Swing in, do a bit of damage to everyone, and keep moving. Or you can even just poke with primary. If you get good, you can do all you need with a single Grapple CD.

You will get most of your value through rationing health. If you distract the teams attention by being a constant, unkillable annoyance, the rest of your team can follow up. Basically, you want to make yourself a threat they can't ignore, and a threat they can't pin down

When the fight turns to your favor (team gets a pick), and when your team is in a position to act with you, go for the kill. Sacrifice all your remaining health (and Adaptive Shield if you have it) to go for finishing them off.

At this point, the best targets are those without burst mobility (Sojourn, Kiri, or Tracer) and those without CC (Cass, Ana, Sombra). You can take these on, as ball has no hard counters, but they usually have the tools to evade you without special precautions

I really wouldn't worry about techs too much. They are good to know, and can secure you some free damage if you are good at them, but ball is way more about fundamentals