The only thing that you want to change here is the awareness level of new releases. One can set this to "supported" (regular) releases, "long term only" (LTS) releases, or even "nothing" (no major upgrades).

The GUI way of setting this op is mentioned in the answer of Im'juz ChanYun, but for command line, this is changing this file: /etc/update-manager/release-upgrades:

# Default behavior for the release upgrader.



[DEFAULT]

# Default prompting behavior, valid options:

#

#  never  - Never check for a new release.

#  normal - Check to see if a new release is available.  If more than one new

#           release is found, the release upgrader will attempt to upgrade to

#           the release that immediately succeeds the currently-running

#           release.

#  lts    - Check to see if a new LTS release is available.  The upgrader

#           will attempt to upgrade to the first LTS release available after

#           the currently-running one.  Note that this option should not be

#           used if the currently-running release is not itself an LTS

#           release, since in that case the upgrader won't be able to

#           determine if a newer release is available.

prompt=lts

Once you set this to prompt=normal you'll be notified (and allowed in a regular way) to upgrade to a regular release. Do this only after you've upgraded to 12.04 directly, as it's the fastest upgrade path. You really want to avoid the path in the first line here:

10.04 -> 10.10 -> 11.04 -> 11.10 -> 12.04 -> 12.10 (if you would select normal now)

10.04 ----------------------------> 12.04 -> 12.10 (if you select normal after 12.04)