Ok, sorry for the lateness...
I have found that using DarkTremor's A2SD Script for App2EXT on CM Nightly's is really easy, not so much trouble and just smooth without so much hard work.
Ok, this is really quick and easy.
ASSUMPTIONS
1. You have rooted your N1 (there are plenty of guides out there for this, so I won't go into those details).
2. You have installed a Custom Recovery (Amon_RA or Clockwork (easy via ROM Manager))
3.
NANDROID BACKUP
Steps:
1. Backup your SD Card, I mean
EVERYTHING that you want to keep, back it up.
2. Reboot into Recovery
a. If you have not done a Nandroid Backup, do it now
3. Partition your SD Card using RA or Clockwork Recovery with the following in mind
THIS WILL WIPE ALL DATA ON THE SD CARD (the reason for step 1):
a. For the Nexus One, you do
NOT need a Swap Partition, so set that to 0
b. Personally, I use a 512MB ext partition, but I (personally) won't go more than 1024 MB (1GB).
c. Remember that when you create the ext partition, it will be ext2, remember to upgrade it to ext3. I would
NOT suggest ext4
UNLESS you know what you are doing and the ROM explicitly states that it is supported!!
4. Use the USB Support in the Recovery (or ADB) to put your ROM .zip files onto your SD Card.
5. Wipe all data to prepare for flashing (User Data/Cache/Dalvik Cache/ext part/Battery/anything else).
6. Flash your ROM
a. If you are flashing Cyanogen, remember to flash the GAPPS .zip as well
7. Flash the DT A2SD Addon
8. Reboot
Set up your phone as normal once you boot up. Let everything sync. On boot up, the a2sd scripts will see the ext3 part and auto-install everything there, so no more work to do from here.
The only additional thing I do is move my Dalvik-Cache to SD.
To do this:
1. adb shell
2. su
3. a2sd cachesdreset
This will move it and reboot your phone.
I don't suggest moving to /cache part since it is only 90MB and can cause instability if you do a lot of data on your phone.
Sorry for the scribble tut, but at work and have work things to do...
Hope this helps!