There aren't a whole lot of tips or tricks that I can think of for .cmx files. Just take your time, and proofread every 10 seconds. But there is a place of vast knowledge and information called The Sims Toolbox (where I learned most of everything about Sim making) and he has the actual freeware for writing a .cmx file. Yes, I made you read all the way down here just so you could find out there was a program for this. Haha.

*UPDATED INFO* The Sims Toolbox is no more. But Paladin of Sim Wardrobe has one at his site.

Seriously, I just think it's best for you to know a bit about what goes on and how it's made. If you'd rather use the program, fine. Doesn't make you a bad person. Neither does NOT using it. I don't, but that's because I had been making my own files before the Editor came out. Either way, the mystery of the .cmx file isn't as scary as I used to think, and hopefully it isn't for you either.

Another tip I can give you is don't give up if the thing refuses to work. It took me a month to figure out how to put 1 lousy accessory on my very first custom model. Even now, I do stupid things when making them and have things that refuse to work even though there is nothing wrong with them. That's just the way this customizing thing goes. I had a very kick-@ss Grinch all ready for Christmas, untill the game stopped loading the texture file for his body for no reason at all, making it impossible for me to field test him. Obviously, he never made it out of my PC and into yours, and that's just an example of how imperfect this all is.

Also, any acessory for the head will not show up properly in SimShow. The .bmp for the accessory won't be seen.

And just in case you aren't quite sure where the part should attach to, here is a picture of a "stick-man" diagram which may look pretty bad, but it gives you the idea. Click on the thumbnail for a look. Well, maybe he's more of a "circle-man".....