For technical boots (hiking, alpine, whatever) follow manufacturers instructions. There are compatibility issues between cement and leather care products that can make it impossible to repair if you’ve used certain products.

For traditionally constructed boots, I use a leather lotion or leather conditioner every so often, and generally don’t use wax polish. That’s partially because I’m not looking for a mirror shine, and partially because I have found that too much wax polish allows the leather to dry and crack, especially at the creases behind the toe box.

There’s a lot of information on the internet about how different tanning processes need to be treated differently and that’s true, but mostly unhelpful as it’s difficult to find out what exactly the leather in your shoes was tanned and finished with. If you value your sanity, don’t think too much about it.