Base Texture Creation
First of all I will explain a bit what base textures are. The name is pretty much self explanatory, they are the base of all the other textures, just plain textures with no details, but are very important on any good texture pack, since they give more possibilities to the mapper. Now to start we are going to do a very easy texture type, which are the metal textures. Open a new document with a 512x512 size and follow the next steps.
NOTE: Photoshop 7.0+ needed, some steps may not be possible in older versions
1. First of all let's select the colours for the texture. The easiest way to do it is to use the colour swatches, which can be found on the 3rd panel on the right in your Photoshop. To use them just click the swatches tab
(window>swatches), then click on your background/ foreground colour to open the colour picker, and then over the desired colour. For this example I'm using Foreground: #3D3D3D Background: #666666, which are two dark greys.
2. Go to FILTER and select RENDER > CLOUDS, this will give some randomness to our texture look. Then select again the FILTER menu and then ARTISTIC > SPONGE. On the sponge options put the minimum value for all fields, which will be:
We do this because we don't want to add to much detail to the texture, trying to keep it very smooth.
Now to finish this step go to the IMAGE menu and select ADJUSTMENTS > BRIGHTNESS/CONTRAST and decrease both values, in my case -30 for brightness and -50 for contrast, but you can experiment with these values as long as you keep the texture very smooth.
3. Now we are going to add some light to our texture. For this we are using the DODGE and BURN tools (hotkey o). This two tools work the same way as the brush tool, but changing the light values instead of the colour. The dodge tool makes it lighter and the burn tool makes it darker. So now we need to define our light source, in this case I assume the light comes from above, so I'll dodge the top and burn the bottom. Use the airbrush brush, with the maximum size (300px), put the exposure to 20, and the range to MIDTONES, for both burning and dodging. Try not to make it to dark or to bright, smoothness is the keyword. Don't forget it.
4. We already have a base texture but it looks a bit boring, so we are going to trash it a bit to make it more realistic. For that select the BURN tool again, using a 1px size brush, and a low exposure around 20. Then start making some random scratches all over your texture.
5. Last step, is to sharpen our image, so go to FILTER>SHARPEN>SHARPEN, repeat it one more time and that's it.