The flute should be cleaned thoroughly inside (using a regular cloth) and outside (using a microfiber cloth) after each play. Especially silver flutes, but also lower gold alloys, tend to tarnish quickly, mainly due to any grease residues from the skin.
To do this, detach the head and foot joint exactly as you assembled them. Initially, place all three parts back into the case - this is the safest way to store them. Wrap a cotton cloth around the cleaning rod, ensuring the flute's inner side won't get scratched. Then take out the parts one by one from the case and clean them as follows:
The keys contain 'pads,' which are made of elastic material (a cardboard layer, felt, and a thin membrane called fish skin). These pads seal the tone holes airtight. Since pads are very delicate parts of the flute, they should never be touched with fingers or a cleaning cloth. Some professional flutes nowadays use synthetic materials for the pads, offering less tone damping, better resonance, and greater durability (like Straubinger Pads, JS Gold Pads, etc.).
Over time, silver on most flutes tends to turn black in some areas. You can gently clean your flute with a silver polishing cloth. However, it's advisable not to do this too frequently, as it gradually removes some of the silver plating. Avoid polishing the keys as they bend easily, and there are small springs and axles nearby that can be easily bent. Have this done by a professional.
The flute has a delicate mechanism that needs to be oiled and adjusted. Pads are replaced when worn out. Leaving the flute assembled for too long should be avoided as it can gather dust or even rust. It's best to avoid leaving the instrument near an open window, in direct sunlight, or on a heater as the pad leather can react to temperature and humidity changes. Also, don't store cleaning cloths in the flute case, as this may cause dust to accumulate on the flute faster, and the pads may absorb moisture and suffer as a result.