Learn Italian: Facciamo molta attenzione. - We pay a lot of attention.

Exactly! In English, you "pay" attention, but in Italian, you "make" or "do" attention. The set phrase is fare attenzione. To say "we pay attention", we use the "we" form of fare, which is facciamo.

Is facciamo irregular, or does it follow the normal rules for verbs ending in -are?

Fare is a highly irregular verb. While the -iamo ending is the standard "we" ending for Italian verbs, the stem changes completely. Instead of building on "f-", it builds on "facc-" (from an older Latin root). This gives us facciamo, which is a form you will just need to memorize!

Why is the word for "a lot" written as molta instead of molto?

The word molto changes its ending to match the gender and number of the noun it describes. The noun here, attenzione, is feminine and singular. Because of this, molto must also become feminine and singular, giving us molta.

Where is the word for "we" (noi) in this sentence?