Useful things to know overall
1) Unpack batteries from found PDAs before selling them to various faction NPCs.
2) Don't rush to accept every fetch quest from every Stalker you find before you have the item they need. Wait until you've gathered some loot and then ask around if Stalkers want the items that you're sure you have stashed away. Otherwise, the Stalker who's waiting too long for your delivery can wander off, potentially get killed, and the mission will fail, resulting in reputation loss.
3) Barkeep and Professor Sakharov regularly request artefacts and mutant parts. Consider stashing that stuff next to them.
4) Trade with Stalkers you meet for a chance to find unique documents (Anomaly Maps) that will reveal location and anomaly information. They are quite rare but not overly expensive, costing several thousand RU.
5) In order to obtain the recipes needed for "purified" mutant meat, find Spirit in Yantar. If you give Spirit enough Nemiroff vodka for him to "reward" you with equipment or ammunition, he will also hand you his handwritten notes on how to safely cook mutant meat with copious amounts of vodka. [kudos to JerryAnderson "Fang"]
6) Consider saving all your found alcohol (named vodka and beer for Spirit; metal bottles as possible fetch requests for NPCs), or selling it to bartenders, and instead use cigarettes as a means to heal radiation when exploring. Multiple stacks of various tobacco products (plus the required matches) weigh nearly nothing, whereas a bottle of alcohol start at about 0.70kg each.
7) Artefacts can sometimes accidentally spawn slightly under the terrain. If your detector shows you an artefact that you can't see, try throwing a grenade in that general area to dislodge the artefact from the terrain.