1) Don't - I repeat, - change items 254 and 255. They are data related to the Twoson Department Store, not valid item slots... I once edited these, and not knowing how to fix what I did, it took me a month to copy all of my changes to a ROM that wasn't screwed up. You probably shouldn't change item 0 either.
2) Be careful with the pointers! If you point to an invalid block it will probably blow up your emulator right then and there.
3) Watch your length. The naming fields are almost universally 24 characters long, but sometimes that won't fit in the screen in the game. Think about how it would look before you apply your changes.
4) If you're creating an IPS, always used an UNCHANGED EarthBound ROM as your base file. Also, never apply your latest IPS to your hacking ROM. It can lead to bad things.
5) While this isn't a PK Hack-related thing, be civil on the forums. Try not to bash others' ideas too much, don't start flame wars, and watch it with the demands. Asking for something nicely will probably get it for you. Demands will get you ignored, or reprimanded if you're making them incessantly. Threats will get you - as James Joyce aptly put it in A Portrait of the Artist as a Young Man - "a toe in the bum."