[Kyocera Zio M6000] br0adband:
I just got a Zio 2 days ago, and the basic process is this:

1) Get ClockwordMod Recovery for the Zio here - follow the instructions in that post, to the letter - but ONLY when you're actually ready to get the ROM installed because you need to copy it to the microSD storage card *first* so CWM can install it.

2) Get OpenZio ROM 2.1.2 from here - download it, but do NOT extract the Zip archive. It needs to remain a Zip file.

3) Plug in the Zio making sure you have a microSD card in it that can hold the OpenZio ROM archive (openZIO_ROM_2.1.2_Spz0.zip 81MB) - hopefully you're using something like a 2GB or larger microSD card so you've got space. Copy the Zip archive to the root of the microSD card (makes it easier to find).

Also note: this ROM does not run off the microSD card like some phones are capable of, the Zio can't do such things, at least that I'm aware of.

4) Once the ROM archive is copied to the Zio, and while the Zio is still plugged into the computer (because you're about to use the boot over USB capability it offers, aka fastboot), shut the Zio down completely.

5) When the Zio is powered off, press the Send (green) and Power (red) buttons at the same time and hold them for roughly 10 seconds or so, might be less on your phone, I don't know. What you'll see is the Kyocera logo (probably) on the screen and some white text in the upper left side.

When you've waited about 10 seconds, let the Send and Power button go. If everything is working properly, your computer should notify you that a USB device is now attached - with Windows you'll get that "duh-dunk" sound.

6) Follow the instructions for Clockwordmod Recovery as noted in step 1 - now is when you follow them to the letter. Open the command prompt, change to the directory, run the command:

fastboot boot clockwork-recovery.img (press Enter)

After a few seconds it should finish the process on screen (on the computer) and you'll note activity on the Zio itself, after a few more seconds you should see a blank screen with green text options at the top. Use the Volume control buttons to move up and down the selections, use the button under the scroll ball (press the ball down till you feel it "click") to make the selection highlighted.

Use the normal Back softkey to back up a step, etc. You can also use the Home softkey to go back to the main CWM menu at any time.

6) Choose the "Install from zip" option, browse for the file the openZIO_ROM_2.1.2_Spz0.zip file in the root of the microSD card, say yes to the confirmation messages, and wait for it to flash the ROM. When it's done, press Back or Home to get back to the main CWM menu, then select "Reboot the phone" and that's about it.

It should reboot into OpenZio 2.1.2 from that point on. If you don't see the somewhat familiar green Android with the glowing silver-gray circle and the green-swishy water pattern, well... I didn't the first time I did this until I read someplace that OpenZio is best installed on a device that has just been freshly restore to the stock 2.2.1 image from Cricket - as Spz0 said in the OpenZio thread, this ROM is for the Cricket Zio but it might work on the Sprint model. It's your choice to try it if you've got the Sprint model.

Because I wasn't getting any noticeable improvements in performance, I decided to go back to the factory Cricket Zio image (found here and THEN I installed OpenZio and THEN I noticed a boost in most everything. :)

So, the proper method is make sure it's got a factory/stock 2.2.1 installation on it, then install OpenZio 2.1.2 on top of that, and when it boots the first time (it'll take longer, of course), you should see that little green robot and then swirly water mist thingy... you're good to go if you do.

Hope this helps... ;)