iam gonna keep it short:

you can change your outfit in the first saveroom (wardrobe)

of course you can smash crates, vases for items with your melee weapons (always do that)
sometimes you can open up trunks from cars for items.
when you get the big hammer, smash those walls (2 are story related) the other 2 are in the first area convent (near the kitchen) and cemetary (crypt with 4 horsemen)

you find a metal detector later on, use it again near statues that show you a direction..you will find extra loot

think about upgrading your weapons with stuff you find (to build the crossbow, use bicycle parts on it for example)

that,s all for now..hope it helps one or another.