First I want to thanks Smithycpl for his help and valuable input! Without his help I would not have had part of it right. I also figured these things out by studying the codes quite extensively.

This tutorial is not for a beginner. I have written it in a step by step and hopefully easy to understand manner. Please understand that creating a global mod can cause problems for your game especially if it’s not done correctly. I recommend that you back up all your game files before you attempt this project.

I've also included a finished global hack that gives hunger and fun when sims get a drink of water.

I also want to thanks Echo for all her great tutorials on modding. I've learned so much from her.

Very nice. I'm sure this will be well appreciated by all the people eager to try their hand at global mods.

It's very good written and easy to follow Rebecah!
Thank you for this tutorial.

I have a question. I know, questions, questions, always questions.
I wanted to create a bathtub that visitors would use without actually being invited to spend the night. I imported the bhav 2000 which is the global test bhav and then added it to the rest of the bhavs, thinking that once it was part of my guestbath.package, it would lose it's globalness. Wrong, now all my bathtubs allow guest bathing. So what do I need to do to change the bhav to operate only on the package it is in? Can I just change the 2000 to something else or will that mess up the other bathtubs.

Edit: OK, I changed the Instance to 1010 and the group to FFFFFFFF and I'll see how that works.

Thank for this tutorial, I will try =)

Although I hate having to code (I stay away from it), I want to create an autonomous whoohoo (not try for baby) for The Sims 2... someone made a Sims 3 version, but I don't have that yet.
I might try this out later, if I can get my butt to start coding.

The tutorial looks intresting, hopefully it can help me figure out a way to make a mod that prevents food from randomly being burnt when cooking.

Hi!! Can I make (with your tutorial) global mod for my Sims: to them to have a hair on their bodies? Please, answer. I made some skins in The Sims 2 Body Shop, but they are shown in game as "Custom Skins". Please help!

DJ, what you're describing is a "default replacement skintone". It's similar to making a regular skin in body shop, but you need to do some work in SimPE as well so that it overrides the standard "default" skins for sims

It's related to Bodyshop modding, so you might like to head over there for details:
http://modthesims.info/forumdisplay.php?f=444

Good luck! :D

Sorry for not replying for over ... 9 MONTHS??

OK, so those are default replacement skintones... good, then I'll search for them... thanks!

What is a Global Mod?

Here's how the Upload Wizard defines them:

Global Mods: Mods that run in the background that modify game play in all lots without player intervention.
Object Mods: Individual objects with customized pie menus and options.
Config Mods: Modified configuration files that are not packages.

I would like to create a mod that children can use the Hot Tub.