To make a npc, i good idea might be to figure out what type you would like to make. The 1st thing i would start with is to make the npc in your database. i find it easyer to go in the game and find a npc of the type i wish to make and go into the DB and copy, and paste it in notepad. change the id to what ever # you want to use: i find 60000 is a good # to start with exp:
60000 25079 Tony 1 Gm Weapon Shop 1 Monster.cutie_cat 8 15 70 male L2Merchant 40 3862 1493 11.85 2.78 40 43 30 21 20 10 0 0 1314 470 780 382 278 0 333 0 0 0 88 132 NULL 0 0 0 LAST_HIT 0 0 0 fighter false
as you can see this type is an npc that will sell you stuff from the L2Merchant in its list. there are others like L2Npc, L2Walker, and many more. this part will tell the server how to read what files when a player opens the npc's menu. If it is this type of npc it will open files in the merchants list in the Html of your server pack. If it is an L2Npc it might open a quest section.
so the next thing i would say to do is get an under standing how the server will read the server pack you have, as you play around with npc you will get an understand how this works. open up your Html file in your server pack. you will see there are lost of files like teleport, merchant, default, and so on. if you go in your server and hold the shift down and click on an npc it will show you what type it is.
after you know what type of npc you want or need, the next thing to do would be make a Html file for it to read, this will be the first file the server will read to show your players a menu, so they can pick what they want, as in what grade of armor they want: Dgrade list or c grade list and so on. an understanding how to work with html scripting is a must, but again by looking at other ones you can figure it out.
next after you have made you first menu's and links, you want to make a XML that will hold the items you want to sell or trade here is an exp:
<!-- Greater Dye of CON <Con+4 Dex-4> -->
<item id="1">
<ingredient id="57" count="1000000"/>
<production id="4616" count="10"/>
</item>
this is a very bases on how to get a good idea how it works, my best advise it to do some research be for you start, i found making npc's can be very upsetting at time, mostly when you forget to add one small thing or set the right #.
I how this helped some.
haha..