That is a great question. To avoid margin call – the advice is to both maintain a surplus of funds at all times to prepare for any extreme market movements that may occur (i.e. always have more than enough cash) and to keep losses and the size you trade to a comfortable level. i.e. don’t trade 1 lot with $1000 in your account.
I cannot offer specific advice but generally the higher the size of leverage and the less in the account, the greater the chance of a trader running into trouble.