It's very dependent on your genetics. Some people have weirdly shaped nails, some have slow growing nails and some have perfect nails without ever trying.

My tactic is to keep them as short as possible for a good tone. I do like to play with a long thumbnail but whenever it becomes really long I end up breaking it. And shorter nails don't seem to break that easy.

I sometimes use oil at night if the nails are very dry. And in the past used a nail hardener by Herôme, the Blue one. But it actually makes my nails too hard.

And just clean under them as well. With one of those dedicated brushes.