[Transformer TF300T Q&A, Help & Troubleshooting] diesburg:
I can TRY to help. I have no mac, never used one, dont know the procedures for getting the drivers and stuff installed on mac. So, im going to assume you have the fastboot drivers installed properly.

NOTE: IF YOU'RE TABLET BREAKS, NEVER TURNS ON AGAIN, OR GOES UP IN SMOKE BECAUSE OF MY DIRECTIONS, IT'S ALL YOUR FAULT AND RESPONSIBILITY NOT MINE. GET OVER IT AND BUY A NEW ONE.....LMAO.... really though, i am helping as best as i can and you always run a risk flashing devices and thats your risk, not mine.... but if you follow my directions exactly, you will be jsut fine and not have a broken device...

First, make sure you're on the latest update from asus. Should be a bootloader ending in 15.3 and android 4.2.1 .

Second, unlock your bootloader. Unlocking the bootloader is quite simple. Download this: http://d-h.st/86c Install it on the tablet and open the app (its a RAR file so it needs extracted first) Follow the directions it gives you, if i remember correctly, you just click yes or something, tablet reboots, and the bootloaders unlocked. If it sucessfully unlocks, when you first turn the tablet on, in the top left corner of the screen, it will say unlocked.

After bootloaders unlocked, turn the tablet off. Power on the tablet by holding the power button and the volume down button at the same time. This will take you into bootloader mode. One quick thing to make sure you are on the latest bootloader. The bootloader screen should have 3 icons to choose from, if it has 4, you are on the old/wrong bootloader and need to go back and update your system before proceeding. If 3 icons, you're good to go, plug the usb cable in the tablet and in your computer.

Download TWRP recovery now. This is the part where you dont wanna screw up, downloading and flashing wrong recovery can equal a broken tablet. Download this exact TWRP recovery: http://diesburg.co/tf300t/twrp/openrecovery-twrp-2.5.0.0-tf300t-4.2.blob

Put that file in the folder where fastboot is.

Now in your terminal/command line, go to the directory where fastboot is. With tablet plugged in and in bootloader mode like mentioned above and terminal in the fastboot folder, type: fastboot -i 0x0B05 flash recovery openrecovery-twrp-2.5.0.0-tf300t-4.2.blob and press enter .... this will flash TWRP recovery to your tablet using fastboot.... if you get something like "waiting for device" in your terminal window after typing this and it never gets past that, thats where i cant help, drivers for fastboot or something isnt right.... if it works, hell yea, onto the next step....

Reboot the tablet, type: fastboot -i 0x0B05 reboot and press enter.... let android fully boot up, copy your ROM to your tablet and dont forget the gapps package for the rom..... now turn the tablet back off......

power the tablet back on like before holding power button and volume down.... once in here, RCK will already be highlighted, if its not, use your volume down key to get it highlighted... once highlighted, hit volume up and this will boot the twrp recovery you flashed......

Once in TWRP, (FIRST DONT FORGET CLICK BACKUP AND MAKE A BACKUP OF YOUR CURRENT ROM!!!) now, make sure you can see your cyanogenmod rom file and gapps by clicking install and going to the ocation where its at, if you see the 2 files, click the back button to the main screen.... on the main screen, click : Wipe, then click factory reset.....after that, go back to the wipe screen, and click system to wipe the system partition..... now go back to the main screen again....

Click install, then click to install the cyanogenmod rom.... after it installs, install the gapps package.... after that, you SHOULD be good to go, reboot the tablet by clicking reboot to system.....

I think that covers everything..... now in the future for flashing other roms, always wipe before flashing and flash the roms the same way you did this one.... just so you know, not ALL roms require gapps package.... most specify whether they do or not....

Any problems, let me know unless its the "waiting for device" thing, i cant help with mac drivers, someone else will have to