Ok, with the new update the stalk market is probably one of the best ways to make bells.
There selling prices follow one of four patterns every week.
Prices change every morning (when re-tail opens) and at noon exactly.
The four pattern types are: Random, Small Spike, Large Spike, Constantly Decreasing.
The random pattern is as you can guess random. It never really goes over 200 bells, but is over 100 bells at least once or twice a week.
The Constantly Decreasing pattern starts at 75-100 bells usually and decreases with every price change.
The Small Spike pattern is a decreasing pattern but will have a set of four consecutively increasing prices, followed by one above average decreasing price. The maximum price is the fourth increased price from this pattern and is at latest Saturday morning and at earliest Tuesday afternoon.
The Large Spike pattern is what you want to see. It also features a decreasing pattern but it has two consecutively increasing prices followed by the maximum price for that week and then two above average decreasing prices. The maximum price is therefore any time but a Monday or Saturday. (The highest I've seen is 517 bells per Turnip, the reason this is the best way to make bells now).
There is a fair risk of losing bells, however, it can be avoided by playing with others who also follow the stalk market (that would be me and most likely others from this site) as their patterns aren't necessarily the same as yours. (I could have a large spike this week while you could have a constantly-decreasing pattern this week.) You can sell your turnips in other people's town.
Risk of losing bells has nothing to do with how many you buy, so whatever you put in you must try to get back out at some point that week, as any leftover will spoil at 6AM Sunday the next week.
My tips on when to sell. Basically, wait for an increase. If it decreases straight after an increase, you have a random pattern, so just try to make any profit at all. If you see a second consecutive increase, you have a spike pattern so wait until the third or fourth increase before selling. If the third is generally above 250, sell because you most likely have a large spike, if not wait for the next price change and sell because you have a small spike pattern.
That's basically everything you need to know about the stalk market, if you're still confused I got most of my information from the web awhile ago so you could check there as well.
