I have a mini tutorial on flickr somewhere on preparing photographed textures for use in 3d applications but can never find it so thought I would write it up properly for the blog.
These days I mostly take photos of individual textures rather than a whole wall or floor as there are so many great plugins like mightytiles, VP walls & tiles and multitexture that can take care of the randomisation for you. It makes the initial process of capturing the textures a lot easier for sure.
First thing I do is to run the photos through lightroom and make sure the color balance is the same on all raw files. Then I use the automatic straighten to try to square up the photo or the manual perspective tools if that fails. I then crop in lightroom and sometimes use the spotting tool to get rid of unwanted imprefections. Note that the colours are still a bit wild due to the uneven lighting, that can be fixed later.
In photoshop, i then open the TIF that I exported, duplicate the layer for comparison purposes, then do a high pass of about 100 (radius) on it.
IMMEDIATELY after doing this, go to Edit>Fade High Pass change the mode to Luminosity and leave the opacity at 100% and hit OK. This brings back some of the colour info from your texture.
If at this point you are making a seamless texture, then you would use the offset filter (Filter>Other>Offset) and offset the image half of the resolution to the right and downwards, then tidy up the seams using whatever means you prefer.
Usually I am trying to match reference images for materials so a useful trick to get the colour right is to use the match color tool
and then select the source reference image (open it first in photoshop) and adjust the sliders till you get a decent match. Even if not matching a specific reference image, this step is great to make sure all your textures are harmonious in colour.
That's about it! Usually when making a Mighty Tiles texture I'd try and have 8 or more fairly high res textures.
PS. I have tried every seamless texture maker plugin going and never really liked any of them. Same goes for bump & normal map making programs. I always get better results taking my own photos and then trying to come up with a clever way of making a displacement map for it, if needed.