The best thing to do with coins you have mined is store them of course. You can also sell them but why are you mining then
just for the money or in the hope you will get rich out of the coins you've mined. So i prefer to hold them and wait for
the best selling price.
Depends on what coin you are mining/in which way. I'm mining using Nicehash, hence, the payment is made in BTC, therefore,I can only save them and hope BTC's price increases, which happened when I saw my balance to greatly increase after the recent pump. I am planning to start mining without Nicehash soon.
Although, the way to maximize your mining earning is by holding what you are mining, especially if it's a promising coin and not some stale one (Dogecoin for example is mostly stale, not fluctuating). At first, your earnings might be low in terms of Fiat currency but there's a chance the coin's price to vastly increase in the future.