I always trade minimum lots. that helps me not to interfer into my risk management. I recommend all the newcomers to trade min lots, as it's safer.
It is up to your capital how much lot is high or minimum for it . For thousands of capital one can use standard lot and up to $500 capital he need to use mini lots. With this way he will reduce risk in trading. maximum lot should avoid . Trader can gain profit again with minimum lot but loss recovery is quite difficult using big lot size.Minimum deal volume depends on your amount of money and the amount of profit you want to get. But the more important question is not the minimal deal, but the maximum deal, because it's very risky.