https://media1.tenor.com/m/4BRF8qhc7RYAAAAd/but-why-ryan-reynolds.gif

Good ventilation is the main one I'm aware of. Hydrogen is only flammable when there's a particular range of mixture with oxygen. If it's too dilute then it won't burn, and the same in the other direction with not enough oxygen mixed inside the hydrogen. So a leak that goes straight into the outside air is not really super dangerous, the hydrogen shoots up and away and quickly dilutes to non-flammability.

In Hindenburg's case there were multiple internal gas bladders contained by the aerodynamic outer envelope, held in place with frames and with walkways and other gaps between, so there were a lot of spaces for a mixture of air and hydrogen to accumulate and reach the right mix to burn. They had no way to reliably detect that this was happening, back then they didn't have sensors and relied on crewmen literally walking around listening for hissing sounds or "shimmering" air where gas of different densities were mixing. Since Hindenburg was originally intended to use helium lifting gas it wouldn't have been a problem, but switching to hydrogen should have caused a complete redesign to eliminate these internal spaces and ventilate better. And in a modern airship sprinkle the thing with sensors so you can immediately know if there's a leak.

The actual ignition of the Hindenburg is thought to have been due to a static discharge spark. Hindenburg's outer skin was somewhat insulated from its inner framework and the air and ship were charged due to a thunderstorm that had recently passed by. When the crew dropped ropes to the ground this grounded the inner framework and caused sparks between the outer envelope and the framework as it tried to dump its charge into the ground as well. Again not a problem for a helium airship, but something that should have been subject to a redesign for a hydrogen one. Make sure the whole ship is properly grounded and then there won't be charge differences to cause sparks inside it.

Note that there's a theory that was proposed a while back that Hindenburg's outer envelope was super flammable in its own right and was the actual source of most of the fire. It was made of cotton painted with cellulose acetate butyrate along with iron oxide and fine aluminum powder - similar in composition to thermite or solid rocket fuel. But tests were done with recreations of the material and although it was indeed flammable it didn't burn anywhere near fast enough to account for the speed with which the Hindenburg was destroyed. Probably still something to avoid with modern materials, though. Don't make your hydrogen airship out of stuff that could catch fire.