how to clean install 10.7?

You should not replace your main OS with Lion as it's still in very early beta stage and may not be stable and support all the apps you need. Create a partition with Disk Utility and install it there. That way you will have both, 10.6 and 10.7.

I installed Lion on my Mid 2010 mac mini server and 2008 MBP.

The mac mini doesn't have an optical drive, so i used a spare external USB hard drive, created a few partitions (must be GUID) on it and then restored Lion dmg contents to one of those partitions (all done using Disk Utility). You can then boot the installer by holding alt/option key on startup and selecting what you just restored. If you created a few partitions on the USB HDD, you can even install Lion back to one of those partitions on the USB disk and boot of it rather than the internal hard drive of your Mac if you prefer (i didn't).

It was so easy off USB that I repeated the process on my MBP.

Lion is very stable. I'm very surprised.

I used Disk Utility to partition my internal HDD into two partitions, one for the existing SL installation, and one for the coming Lion installation.
I then used CarbonCopyCloner to clone the DMG's contents to a USB thumbdrive with 4GB capacity and installed Mac OS X via that thumbdrive without problems.
To do a clean install, you might be able to use these steps: Clean Install of OS X 10.6 Snow Leopard

littleasian said:

hrmm that sounds pretty easy but i don't have any spare external's lying around. do you have any idea how i would go about doing this with a dvd-r?

Click to expand...

Not tried it personally with Lion, but it should work if you burn it to DVD with Disk Utility. Just hold C on startup.

If you wanna do a clean install:
after the language choice, click on Apple menu and chose "quit install" ( at least I think is "quit install" since in Portuguese this is the meaning...) In the following window chose Disk Utility and run it as usual if you wanna send your SL back to Himalyan! as I did). After the erase process, close Disk Utility and click in install Mac OS X!!!!