This guide is copy-pasted from my sticky at DRN, so sorry if parts of it don't make sense, lol. All I have done is changed the forum code tags to html. Any questions/problems can be posted here-
http://d-r-n.com/phpBB2/viewtopic.php?t=292&sid=9fae5d3b96d9de9b8ffdf93cec689b4b. You will have to be a member to view it though.
This guide was written quite a while ago, I am planning on rewriting it.
First of all, you need LNZ Pro. If you don't already have it, you can download it here- http://sherlocksoftware.org/page.php?id=14
Now, open up Lnz pro, and look in C/Program Files/Mindscape/Babyz/Resource

right click on babyzrez.dll and select 'copy',
then right click on a blank space and select 'paste'. You have now created a blank, unedited back up copy. This is VERY important.
Now, open up your babyzrez.dll. Do NOT edit the copy you just made!
click on the cross beside LNZ and you'll see a list of options. for the time I'll be using WG, which stands for White Girl (2 ponies)
now, this will make no sense at first but it does get easier with practise.
I'm starting with the basics.
1. Eyelid colour
to change the eyelid colour of the baby you are hexing, look at the start where it says

change the 48 to a colour of your choice from the babyz colour chart- http://boardwalkerz.com/carolyn/downloabx/tutorials/BabyzColours.htm
and your new babyz will have a nice new eyelid colour!
2. Eye Colour
scroll down quite a lot until you find:

all the paired numbers (NOT the 68/69's) should be changed to a colour from the chart, eg number 123 is a nice dark green.
3. Hair Texture
scroll up a bit from the eye colour until you find

To change the texture to a game bmp eg B_Blond1, replace all the B_whatever.bmp with the texture you want. The game bmp's are shown here- http://www.juney.co.uk/abs/gamebmps.html
If you want to use a custom bmp, replace the art/autobuild/B_whatever.bmp with resource/clothes/nameofbmp.bmp

like when hexing clothes. :)
4. Hair codes
This is where it gets a little more complicated, so don't worry if you don't get it the first time.
scroll back up to the addball section until you find this-

there are two parts to the code, because there are two ponies on the girl's head. To give your girl a side pony, simply delete the second part so you just have

If you want to use a released hair code, for example my full fringe code-
63, 60, -40, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 60, -30, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 60, -20, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 60, -10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 60, 0, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 60, 10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 60, 20, -90, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
;
63, 40, -40, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 40, -30, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 40, -20, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 40, -10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 40, 0, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 40, 10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 40, 20, -90, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
;
63, 20, -40, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 20, -30, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 20, -20, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 20, -10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 20, 0, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 20, 10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 20, 20, -90, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
;
63, 0, -40, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 0, -30, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 0, -20, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 0, -10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 0, 0, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 0, 10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, 0, 20, -90, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
;
63, -60, -40, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -60, -30, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -60, -20, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -60, -10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -60, 0, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -60, 10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -60, 20, -90, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
;
63, -40, -40, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -40, -30, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -40, -20, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -40, -10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -40, 0, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -40, 10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -40, 20, -90, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
;
63, -20, -40, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -20, -30, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -20, -20, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -20, -10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -20, 0, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -20, 10, -70, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
63, -20, 20, -90, 10, 244, 0, 0, 0, -1, 20, 8, 0, 3,
;
simply paste this underneath the 2 ponies code

you can find lots of addball codes here - http://juney.co.uk/abs
If you want to use a linez code-
scroll down until you find

then scroll down further until you see-

simply paste the linez part under the appropriate heading, normally #2.B;Hair- orange side ponytails
the addball part of a haircode will start with 63, linez part of a haircode will start with a number like 138 or higher.

To see and/or adopt your newly hexed babyz, save in lnz pro, and load babyz.
Then find a 2 ponied white girl code from here-
http://www.angelfire.com/mb2/peekabooztwo/girlscodes.htm
for example, 1275-qaaa-lftg-gbd
copy and paste the code into the box, press adopt, and your babyz should be hexed! :) if you can't see any changes, make sure you have pressed save in lnz pro, and make sure you are using the right serial code.
more advanced stuff (addballs, linez, paintballs, skin colour, etc) coming soon!