It sounds like it would be best for you to use App. manager to perform the upgrade. If you insist on using command line tools, you must do the following (specifically in this order):

apt-get update
apt-get upgrade
apt-get dist-upgrade

Despite my warning below, it is very likely you must 'apt-get dist-upgrade' in the case of a Maemo upgrade, because if any new packages are pulled in as dependencies it will not install at all.

(WARNING: You must use caution when performing an 'apt-get dist-upgrade', as it can be possible to brick your device if you allow it to perform actions which compromise the integrity of the system. Only use this function if you know exactly what you are doing!)