Choose your weapon. The proper weapon is essential for killing a Time Lord. The ideal choice is a staser, a Gallifreyan weapon which causes instant cellular death. Other weapons such as swords, lasers and biological weapons can be useful if you haven't got a staser. Time Lords may also be vulnerable to having their surface bacteria removed, as it helps them to survive in alien environments.
Attack your target. Bear in mind that Time Lords are highly resistant to cold, sonic effects, many poisons, strangulation and the vacuum of space.
Attack your target again. Don't be fooled if the Time Lord falls to the ground and appears to be dead. Time Lords can self-induce a healing trance which quickly restores damage to the body. This can easily be mistaken for death, so make sure to hit your target a few times while he or she is down.
Wait. Time Lords possess the ability to regenerate from lethal injuries. The process turns them into what appears to be a new person, with different appearance and even personality. In addition, be careful: strange energy effects are known to manifest during regeneration events. It may be possible to kill a Time Lord permanently by interfering with the regeneration process.
Repeat your attack. Time Lords can only regenerate a total of 12 times, so if you kill your target over and over, you should eventually be able to exhaust his or her total number of regenerations.