Clean Gently. Dust the furniture/rattan accessories with a soft cloth or a damp cloth. Do not soak it in water, avoid using thinners or abrasive creams.
To avoid splitting of the fibres, lift the furniture while moving it.
Treat your furniture with tung or boiled linseed oil if splitting has occurred due to dryness.
Treat mildew immediately by using a strong bleach solution to clean the infected area. Dry the furniture/accessories immediately.
There will inevitably be one part of your garden, patio or outdoor space that receives more sun or weather than other areas. So keep rotating the chair positions as it can help them wear evenly and extend the life of the furniture.