What are some tips you wish you had learned when first starting off?

As we come up on the one year anniversary, what are some things you wish you had known when you first started diving?

To give an example: - General Tips: samples, medals, and super credits are shared - Automatons: cover is your best friend bring a shield to have cover on the go - Illuminate: Be careful of dead-ends in the city environments - Terminids: Stay moving, clear stalker nests asap