Include units at every step
There is probably no habit that a physics student can learn that has a higher return on investment than including units in calculations. To see what I mean, consider this routine momentum calculation: Can't remember the units for momentum? Don't have to, they're already there on the page! This is particularly useful if you are not using base SI units: you don't get confused or forget which units you're using along the way. Better than that, this method gives us a powerful way to check our own calculations. In the next example, I calculate the time required for an object to fall a distance: What!? Metres per second isn't a unit of time! I've made a silly mistake re-arranging the equation; the kind of mistake it's easy for a student to make, and even pros do occasionally. But pros tend to catch such mistakes because they have kept track of the units. That means we can fix it: The unit being right gives us some confidence the number is right....