Sterling silver is the most common form of silver used in jewellery.
It is alloyed with copper ( predominantly ) as silver is a very soft metal.
Using an alloy helps make it semi-resistant to scratching. It is still prone to scratching and denting though, so care must taken when wearing / storing your jewellery.
Tarnishing is inevitable eventually, especially with pieces that are not worn often.
As with most jewellery it is recommended to avoid the following when wearing your jewellery.
If wearing sunscreen/perfume/skincare etc, it is recommended to put your jewellery on last, after these products have dried.
Whilst water by itself is not likely to harm your silver in anyway, it is always recommended to remove your jewellery before washing hands and showering. Soaps and bodywashes etc can have a negative effect on your pieces.
The easiest method to avoid tarnishing is to wear your jewellery often! The friction prevents tarnishing, as do the natural oils in your skin.
If tarnish does happen you can clean your silver jewellery with a silver polishing cloth.
If this does not work, there are many other ways to clean your jewellery such as a mild soap and water solution, baking soda soak, special silver cleaning solutions etc. The internet is full of knowledge and I recommend researching your favoured method further.
Keep your jewellery dry. Moisture is the main factor that speeds up the tarnishing process
Keep it stored in a cool, dark place, preferably in a tarnish-preventive bag ( zip lock bags can work too )
A jewellery box lined with velvet or other soft material is ideal. It helps absorb excess moisture before it tarnishes your jewellery and it helps separates your pieces so that they don’t bump together and scratch.