To upgrade to Ubuntu 10.10 Maverick Meerkat, all you have to do is press Alt + F2 and enter: "update-manager -d", then follow the instructions on the screen.
[old instructions for when Ubuntu 10.10 was in the first weeks of development]
The steps below are only for when upgrading before even Alpha 1 was released (that's when this post was written) so use the command above now!!!
Right now (Alpha 1 wasn't even released yet!), you'll have to tweak some things to be able to upgrade to Ubuntu 10.10. For now there isn't even an ISO available with Ubuntu 10.10 Maverick Meerkat.
Warning: only upgrade for testing purposes! Ubuntu 10.10 Maverick Meerkat is in very early development stages so a lot of things might not work! You have been warned!
This being said, here's how to upgrade from Ubuntu 10.04 Lucid Lynx to Ubuntu 10.10 Maverick Meerkat:
1. Replace every "lucid" coinsurance in the sources.list file with "maverick" and run a dist-upgrade:
sudo sed -i 's/lucid/maverick/g' /etc/apt/sources.list && sudo aptitude update && sudo aptitude dist-upgrade
2. Now all you have to do is run the following commands and you'll upgrade Ubuntu 10.10 Maverick Meerkat:
sudo aptitude install update-manager-core sudo do-release-upgrade -d