The first thing you need is TIME. Capturing an NPC takes between 30min to an hour, depending on your loyalty waves. It takes between 40 and 50 loyalty waves to capture an NPC. Plan on needing an hour and a half for setup and delivery of waves. Do not let yourself be distracted.
You will need to have an open city slot. You cannot capture if you have the maximum number of cities your title can hold. Please check this before you begin.
Next, you will need an NPC close to your city (or a flat you can build an NPC on of the lvl you want to capture.
Troops. You will need a minimum of 100k archers-preferably 150k- and at least 15k scouts. Waves should consist of 10k-15k Archers and 1k scouts.
Heroes-you will need 9 decent heros with attacks ranging in the mid 100's. Its ok to have one or 2 around 100 attack, but most should be near 150. This also means you need a Feast Hall lvl9 and Rally Spot Lvl9. You can use your mayor to attack as well. Just go to your Feast Hall and click "Remove Mayor". While in the Feast Hall, make sure you remove the mount from all your heros. Even if the timing bug is fixed, you want your waves to have a consisant speed.
Research. The higher the research on your Archery, the better. lvl6 is OK. Lvl 8 is better. Lvl10, of course, is perfect. Military Tradition (Attack) and Iron Working(Defense) are also important as is Medicene.
You don't need any buffs, such as warhorn or corslet or penicillin, unless you want to use them.
Planning-The most important part. Once you decide you are ready, click on the NPC you want to capture and select your waves to see how long travel time is to attack. Multiply this x 2(to attack and return). Divide that time by 9 (the number of waves you will send). ***Hehehe-math again*** In a nutshell, if it takes 2 min for your forces to attack the target, the turn-around time is 4 minutes (2min to attack, 2min to return). If you send 9 waves out in evenly spaced intervals you will need to send every 27 sec. Round that to 30 sec and you will have your NPC in about 30minutes!!! Congratulations!
OK-now that you are ready-and you would like someone to help you capture that NPC-please post your name in the forum labeled "I am Ready for my King/Queen". Someone will contact you to help clear the defenses and assist with loyalty waves if needed. Try to have the minimum troops before posting tho.