The DNC has announced where each candidate will be positioned in the first two Democratic debates. I don't know that podium position is really important, but some believe it is advantageous to have a center position in those debates (believing it shows who the most important candidates are). On the first night, the two center positions will be occupied by Elizabeth Warren and Beto O'Rourke. On the second night, those positions will go to Joe Biden and Bernie Sanders.
Here are the podium positions for all the candidates:
On the first night (Wednesday), the candidates are from left to right: Bill de Blasio, Tim Ryan, Julian Castro, Cory Booker, Elizabeth Warren, Beto O'Rourke, Amy Klobuchar, Tulsi Gabbard, Jay Inslee, and John Delaney.
On the second night (Thursday), the candidates are from left to right: Marianne Williamson, John Hickenlooper, Andrew Yang, Pete Buttigieg, Joe Biden, Bernie Sanders, Kamala Harris, Kirsten Gillibrand, Michael Bennet, and Eric Swalwell.