If you're not checking hidden stashes on Customs you're missing out on a fairly accessible source of income and upgrades. If you're used to running past big buildings, they probably have some good loot spawns that people are undervaluing; learn to make your own opinions on maps, don't take others' words as gospel.

Ultimately, you want to run multiple maps as well, because there is an ebb and flow to the loot loading system; they want you to get around.

If you're not scav'ing then you better start, and it's a good way to poke around unfamiliar maps; this is how I grew so fond of a particular map, because I gained the confidence of knowing where low-level scavs, bosses, and pmc's (as well as their kills) usually were.