Get some skills like alcohol trading, this means you can buy more booze and sell it for more making a profit along the way. <- This does work but drinks are now going down in price considerably.
The trick is when looking at the market there is three arrows. The arrow facing upwards is the one you want to look at, the red up facing arrows. These are the goods which are going up in price. Look in the brackets beside them, if its lower or 100% buy them, if higher they may go down before you can make profit. Then wait, the sell price of these will go up.
Say for example, I bought 15 chestnuts for 500 each with a up red arrow up. The best in real life day I came back and I made 1000 profit from each chestnut.