I have been a holdem player since 1994. Much longer than I have been trading. I agree with the similarities and the practice that poker can provide for the trader(beginner or experienced).
In holdem you are going to get a new hand every 1-3 minutes. Thus, a very quick way to practice discipline!
I would reccommend as dottom says to learn the game and treat your bankroll like a business(trading account).
Additionally, I think that the lower limit games more accurately mirror trading. Because at the lower limit games, the players tend to play basic strategy and fall apart from there(your edge). Whereas in the higher limit games, the players tend to be beyond basic strategy and it becomes "he thinks that I think he has these cards, so I'll raise him so that he thinks that I have these cards".
My style of trading allows for it, so, I sometimes play poker online during the trading day while waiting for a trades to setup or pan out. I find that it keeps me focused on staying disciplined in both trading and poker. On losing trading days, poker provides a nice small hedge for me
FWIW the site I play at is
www.paradisepoker.com (i have no connectionwith this site). The software is free. You can play in 'play" money games for free as well. However, you will find that play money games, like paper trading is nothing like the real thing.
Good luck!
Kempo
Note to Gann--Blackjack and poker are very different. In blackjack you are competing against the casino's edge. In poker you are trading against the smiling fish(sucker) sitting next to you, not the house. That is your edge.