How often should I change my strings?
Some musicians say that strings go "false" after some time. No matter what is "correct," our best bet is to change our strings when they start to sound or feel weird to us.
I choose to change my strings once a year. It is especially convenient for me to accomplish this in January since I usually get a set of strings from Santa right before the new year starts.
What strings should I use?
Short answer: I don't know!
It's such a personal thing. Different strings sound different on different cellos with different cellists!
You will have to do some experimenting with different brands and types of strings.
Here are a few links that I hope will help: