http://www.neopets.com/stockmarket.phtml?type=list&full=true
just go there to buy. go to portfolio to see its current price. only buy at 15 and sell high. it's pretty easy, you just have to be patient.
Totals: 60,000 903,000 981,000 +8.64%

Buy 1k stocks a day at 15-17 NP each. Sell at 60+ if you want to stay stable while starting out. Later on try to save and sell at 80+ if you want more profits. To get a god portfolio, it can take a year or more. So patience is a virtue.

Totals: 480,503 7,296,545 8,991,715 +23.23%

Is stocks a specific item or do you mean like randoms items at 15-17NP Each and sell them for more
And where do you check this data anyway

Totals: 480,503 7,296,545 8,991,715 +23.23%

1. Click link below.
http://www.neopets.com/stockmarket.phtml?type=list&full=true

2. Find a stock that has 15-17 np as it's current stock price.

3. Click the name of the stock.

4. Buy 1,000 stocks (Max amount you can)

5. Post your portfolio totals here. (They will be at the bottom of your personal portfolio.)

6. Repeat.

7. Sell a stock when it gets to 60+ each, you'll have turned that 15,000 NP into 60,000 NP.

The selling price is completely up to you. Some people will sell at 30-40nps, while others (myself included) sell at 50-60. It's all up to you. If you have the nps, sell at 50-60, otherwise you can sell at 30-40 so you can reinvest the nps.
Opening price is just what it is, the price the stock opens at. Don't worry about not making a profit immediately, companies on neopets don't go bankrupt and will eventually gain money.