There are foremost two techniques successfully used to help you last longer whether it is during masturbation or partnered sex. These techniques are found particularly helpful if you suffer from early climax (premature ejaculation).
The start-stop technique is the first-line recommended technique and intervention in health care when seeking help for premature ejaculation. It can both help you to prolong the sexual stamina in the moment, and it can work as a preventive technique to prolong future sex.
The idea behind it is simply hands-off.
When you feel like you are getting close to climax, stop completely, wait for the sensation to subside, and then get back on it.
This technique can be repeated as many times as you wish. Just make sure your partner is aware to avoid misunderstandings.
The stop-squeeze technique is the other form of ejaculatory control.
The idea is that you engage in sexual activity until you almost reach climax, then suddenly stop and hold the tip of the penis until the near-orgasmic sensation subsides. Much like the start-stop technique.
This can be repeated once or as many times as you want.