All of my clay has been found on beaches near water.
What I'd suggest is downloading Minutor. It's a mapping program that allows you a view of your world. Not only that but you can also look at your world layer by layer(making finding diamonds or dungeons easy if you so want)
What you can also do and this makes finding anything easier is by altering the color scheme. You can set up different color schemes for different things. What you will want to do is change the Clay to something more obvious. Like Red. Then you can look for red around your map. You will need the whatever code/whatever it is called for Red. Which I believe is this: FF0000
The forums color font actually uses all of them. Just find the color you want and insert it in for clay.
But this might be considered 'cheating' but I like to think of it as my avatar stumbling on a map with clay marked. :biggrin.gif:
But aside from roaming your beaches looking for clay or downloading a texture pack that makes it more obvious it's pretty much all you can do.
Well I mean aside from just saying screw it and edit caly into your inventory. lol
You do know everyone gets a randomized map save for those few people who use saves and seeds. We can't tell you where the best place to find it is because our worlds are different.
Just making sure you know.
If you can't find any clay on the coastlines you might just be SOL... Sorry.
In every single world I've generated- and the SMP worlds I've played on, when I needed clay I would just build a boat and sail out and keep my eyes peeled. I never had a problem of not having enough clay for rather large buildings. Although I did monopolize all the clay within a few hundred blocks of the village we built :tongue.gif:
Just a few hours ago when I was playing my single player world I actually found some clay in the middle of a desert, which was rather unexpected.