For example if you know your wifi card is tricky to get working and later kernels just don't work.

1. Discover the current latest kernel currently installed. Its the one with the biggest number. $ dpkg -l | grep linux-image
2. Become root. $ sudo su
3. Pin that package and the generics. $ echo linux-image-2.6.32-38-generic hold | dpkg --set-selections; $ echo linux-image-generic hold | dpkg --set-selections; $ echo linux-generic hold | dpkg --set-selections;
4. Update and upgrade apt.
   $ sudo aptitude update;
$ sudo aptitude safe-upgrade;