Im no texture making expert, but ill give you what I believe to me the way to make textures and wads, wait keep reading!

First off get your stuff together, you shall need wally and paint shop pro or some sort of paint program.

Now textures need to be multiples of 16, in other words a size that can be divided by 16 evenly, like 64. So always make sure your texture is the right size!

Some texture sizes:

16x16 - smallest possible
64x64
48x80
128x32
128x128
256x256 - largest *UPDATE* 512x512 is possible but not entirely recommended.

Creating a texture

Now im sure you have some idea of what you want, but remember dont have big spots on textures etc as most times textures are repeated and you dont want them looking pants. A big splotch of paint in a texture is going to make it look repeated and rather pants.

So once you have made your texture, save it as a .bmp file. (the name of a texture can only have 15 letters, nothatyouwouldwantabiglongnameforatexture)

So now you have a single image, which is divisible by 16, and is in .bmp form. Now open up wally, Click new and Select halflife package, [wad3] [*.wad]. Now this is your wad file. Leave it open and click on file > open and select your .bmp image. A Window will pop up asking for what form to you want, now you want halflife texture so click that. Now your texture will be converted to the texture format, which is a 8-bit BMP file so im told. Now click copy over your image and then in your wad click paste as new, then enter a name for it and there you go. You now have a texture in a wad, click file save as, and choose a name and a place for your new wad. You can add more images whenever you like (unless wc is open and your using the wad)in the same way.

Animated Textures

Not as hard as you think really, its all in the name, just name the, in the sequence you want them to go. They animate at a rate of 10hz and you cannot change that, even though 10hz is faster than some of your pc's I bet.

For the first name of the texture use +0nameoftexture.bmp and go up to +9nameoftexture.bmp, so it would be something like this:

+0signa.bmp
+1signb.bmp
+2signc.bmp

- up until +9, im not sure if you need to have 9 animated bmps, so find out for yourself. This is obviously a frame of animation, so we have 10 frames, hence the 10hz I guess, so maybe best to use all the frames to get a smooth movement. The textures will continue to animate throughout the game.

Transparent textures

These are really just normal textures with the part you want invisible a pure blue color. The hex number is #0000FF it must be that, and it must be the last colour on the pallette otherwise it wont work!. Ill try to explain how to do it, its not that hard, say you make a picture of a tree, and want the invisible bit to be everything thats not the tree, well say you make it, and you use 18million colours setting, well you wont be able to edit pallette, it has to be 256 colours, so decrease your colour depth, either before or after which ever you prefer. Then edit pallette, now the last colour in pallette could be anything, anyway click it and make it the pure blue colour #0000FF and then apply it to your picture where you need it to be invisible, then your done, save as .bmp. The name of the texture must start with a { for instance {chocowafer, do this in wally or another texture maker, its not important to have the { in until you save it in a wad using wally.

Dont forget that transparent textures need to be a func_wall or a func_illusionary with 255 in fx amount. otherwise it'll just come out visible with your blue bit showing.