Let them rest and use trees. Leather needs a day to dry out between wears, so rotate at least two pairs. Cedar shoe trees go in the moment you take them off — they wick moisture, absorb odour and hold the shape so the leather creases evenly instead of collapsing.
Clean before you condition. Brush off dust and grit, wipe salt lines with a barely-damp cloth, and let them dry naturally, never by a radiator. Only once they're clean and dry do you feed them — otherwise you're sealing dirt into the grain.
Condition, then polish. A conditioner every few months keeps the leather supple so it flexes without cracking. A cream or wax polish on top adds colour and a water-resistant shine; build it in thin layers and buff between coats. Welted soles like these can be resoled when they wear through, so the uppers are worth looking after.
Dry wet shoes slowly. If they're soaked, stuff them with newspaper, keep them well away from heat, and let them dry over a day or two before conditioning — sudden heat is what stiffens and cracks a good pair for good.