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When connecting your battery, connect the positive (red) first and the negative (black) second. When removing the battery, disconnect the negative (black) first and the positive (red) second. Been doing this for nearly 30 years. ALWAYS connect the positive post first.
Wiring several lemons in series (bulb-copper-lemon-zinc-connecting wire-copper-lemon-zinc-bulb) may do the trick. If you can't get a light bulb to work, try improvising a galvanometer to show the voltage. Do this by wrapping about ten turns of thin wire (insulated) around a small magnetic compass to form a coil.