Dead NPC drop their inventory (if any), it is the sprite looking like a sack. Position yourself over it and Use it to check the loot. If gangs are enabled in your game, a good strategy is to loot drops from 3rd party fights. You won't make a living doing that, but you will get better weapons and some free money.
Search the houses while the owners are away, shelves and other containers may contain some free loot.
Citizen buy stuff and earn money in identifiable patterns, stalking a specific NPC and waiting for a good opportunity to strike can be more rewarding than busting in a random office and spraying bullets at everyone.
Beware of cops using ranged weapons, they may carry a shotgun. It's not a very accurate weapon but it can easily kill you in two hits if they get near enough.
When hurt, you can buy health items or sleep in hospital beds, for a price.
Your starting statistics and skills matters a lot. Lock-picking is hard to level-up, but if you put a lot of points in it and train yourself on low level locks, it will reach maturity quickly and you won't be paying for most items anymore.
Weapon skills give marginal bonuses to accuracy (+20 relative percentage max) and are easy to level-up so they are not a primary concern for new players. High perception and endurance builds with high Stealth and Lockpick skills are better builds.
It's possible to outrun hostile NPC by circling around a building. However the best method, for now, is still to change sector.