When starting out in a town, you can choose to remain there as long as you like, and your products will never spoil.

• Each person has a profession and that dictates what they sell cheaper (they Supply) and what they most need to buy (they Demand). Consider what a farmer offers VS a miner VS an idle Nobleman, and consider what they most want in return.
  
• On top of their profession, specific people might mention what they need, which they'll pay more for.
  
• Other merchants are trying to make money, same as you. They're less likely to part with coin in fair dealings, but they welcome coin more than others.
  
• There are Seasons in the world. Watch out for them since they affect supply and demand. Various people will mention how.
  
• Don't expect fixed values for things, but take notes on things you want to figure out the value of.
  
  • Each person values products differently, including coin, and there isn't a standard coin conversion in most cases. You will, over time, develop a sense of what conversions you can get way with depending on the place, especially if you're taking notes.
    
  • Similarly, you never know what kind of a deal you're getting when you're buying a more esoteric item like magical equipment. I don't think you have much hope of nailing down exact values for a lot of more unique items, so my tip is to mostly get these from the direct producers and not a middleman.

Travelling the various markets presents new opportunities, but also costs. In order to find places to travel to, you'll need to possess maps to said places at least once.

• The same way professions have supply and demand, so too do towns. Some towns may supply a lot of a specific product, which presents an opportunity to buy there and move somewhere else without the surplus to sell it.
  
• Some products are native to certain regions, so they may be worth more when sold outside those regions.
  
• Similarly, some products are altogether forbidden in some regions, so it's expected they'll sell for more if you find people you'd be safe trading with without being reported to the guards.
  
• The traders in the game also have their own towns which they visit, some places more frequently than others. If there's specific people you want to buy from or sell to, figure out their routes.
  
• Moving between towns brings three types of costs:
  
  • Travelling costs cover the expenses of moving from town to town. They scale to the distance between towns and the number of horses you have with you to carry your merchandise.
    
  • The taxes are applied when moving to certain towns, and they scale to the amount of coinage you have with you at that time. Talking to fellow travelling merchants may give you some idea on how to lighten the tax burden.
    
  • Guild fees are a fixed amount attached to certain towns with a richer merchant guild presence.
• Each new town may have an associated quest which will present an opportunity of some kind.

As I've played through the game I've learnt a few things by force or by experience. This section consists of my own thoughts and less of a guide, and it will freely spoil the various areas, tips, and some mechanics of the game.

• You can make money from scratch pretty much anywhere, so carrying merchandise far away is not nearly as tough as it sounds. Keep your coinage in merchandise and just earn whatever you need for the next trip.
  
• Which reminds me of my most important tip: Having fun is more important than anything else. I could spend hours trading Boone vegetables and Kai spices in Winter, but I could also travel the land doing quests and maybe getting ripped off.
  
• For a long time I was afraid to make use of merchants because they've got tight pursestrings and I never know what exactly something is worth whereas they do. But actually, they're a pretty good source of specific stuff you're looking for when you have coin on you. Like as not, they're the best ones to spend coin on, especially if they've mentioned they're looking for silver or gold coins.
  
• The people that go around carrying money are the Nobles, some Soldiers/Knights, and Adventurers.
  
  • In towns that have a producer for something they want to buy, you can probably make fine trade just by buying from the producer and selling to the consumer. Merchants can cover most gaps if you have coin.
    
  • Between these three you can sell pretty much all of your merchandise without getting a bad deal (except for Monster Parts?).
• Ascension might be the biggest trading town but I don't like it much. Few producers go there so even if it's rich on nobles and there may be money to be made especially with a spice company, I just don't like staying there to trade. The taxes and fees are exorbitant as well so I just feel a bit stuck if I go there. I prefer towns with farmers and miners around.