The key for a successful rescue is to stay out of danger. Your safety is of utmost importance and always comes first. Whatever you do, avoid putting yourself in danger. There is no need to add yourself to the casualty list.
Good rescue skills enable you to perform an effective rescue and live to tell the story. Assess your abilities in regular intervals. Keep practising in open water or swimming pools under realistic conditions. This keeps you up to speed and alert.
Before you jump in and go for a casualty,
assess the situation, the condition of the casualty and your own safety.
Only enter the water if you have no alternative and can do so safely.
Some types of rescues are safer than others. Escalate your involvement only as far as necessary. Start with land based rescues. If the first is unsuccessful (or impossible), try the next one on the list. Only as a last resort use a rescue tow.