Whenever you want to introduce a new grammar rule, a new tense or sentence structure, consult your list and look for similarities in the languages. You might want to ask teachers of the various other languages for help if you are not familiar with them. Make notes of similarities. They can be the same pattern of conjugating a verb, the same rule for sentence structure or the same use of a certain tense.
Even more important, though, make notes on the differences. Especially when two languages are close, many students tend to use the rules of their better language without noticing slight differences. Put them on their guard for false friends and point out probable sources of mistakes.