problem with plating adherent cells in 24-well plates - (Sep/26/2007 )
maybe you need to give them a higher shot of FBS. sometimes they do settle at the bottom then end up in clumps. maybe buying better plates will help
maybe there are too many cells? or they're not enoguh.
Try to do a plate with different cells concentration in every row/column of well.
you should mantain the same ratio cells/area you use in the flask. ie: if you plate 10E6 cells in a T25 flask, look what's the area of each well (it's written, but now I'm not in lab, I can't tell you) and calculate the cell number with a "proportion":
10E6 : area of the T25 = number of cells you have to put in each well : area of the well
hope I 've explained myself!