Short answer: support is a price where buying has stopped falls before; resistance is a price where selling has stopped rallies before. The more times a level held, and the more timeframes see it, the more it matters — until it breaks.
Look for prices where the chart turned more than once. Mark the area, not a single tick: a level is a zone a little wider than the wicks around it. Then keep only the ones nearest price — the floor below and the ceiling above. Those two decide the next move.
When price closes above a ceiling and stays there, the old ceiling often becomes the new floor. Traders who sold there want out at breakeven, and traders who missed the break buy the retest. The retest that holds is the confirmation; a close back below the old level makes the breakout false.
See live examples with the levels already marked: Bitcoin key levels, Solana key levels, all markets today.
You don't in advance. You watch the close: a candle that closes back above support after dipping under it is a hold; a close below that stays below is a break.
A zone. Mark the area where price turned, a little wider than the wicks, and treat a close beyond the whole zone as the break.
Sellers who were wrong want out near their entry, and buyers who missed the break buy the first pullback. Both put orders at the old level.