Most classes have 2-3 key ranks where they gain some new skill/spell that puts them in a power position. For combat classes you also include 15 for defenses.

When you hit a key rank if you stop for an hour or two killing your current ranking tier -1 mobs, preferably of similar ethos (kill evil mobs if you're evil) then you can get your skills/spells at a decent level without having to dedicate tons of time all at once which tends to make me feel like my character is in a rut.

Common exceptions include assassinate and unholy blessing which means you need to level-sit and get those babies up.