Here is the rule of thumb for distinguishing between the two.
- If the magic in question requires significant time, multiple components, locations or a sequence to enact, then its probably a ritual. Anything simplistic or quick to use, that disregards location, environment and so on, is likely a spell (or equivalent).
- If the magic is requires some complication, measuring or particular exactness to use then its likely a ritual.
- If the output of the magic is something long term (say, > minute), then its likely a ritual.
- Magic to someone something requires the inscription of a magic circle or equivalent protection.
- Magic to create wall of stone, wood, earth, etc.
Now some magic is borderline and the GM will have to make the choice of which path to take. Take the Heavy Helper spell in the system. It makes a permanent pile of sand appear. However the measure and complexity to utilize it is simplistic and the caster has little control over how and where the sand appears other than distance. While permanent, the sand is normal and not introducing an unnatural element, such as bringing forth a wall of fire or ice and keeping it within a certain proportion. So, once created it does what any pile of sand does.
So as you can see, some magic will require you to make choices to place it appropriately. It will just require your best judgement to do so.