Selection of stable transfectants after transfection - (Dec/17/2006 )

I did transfection of MCF-7 cells with a GFP-gene construct yesterday (approximately 20 hours ago) using Lipofectamine, followed by culturing them in antibiotic-free RPMI 1640 +20% FBS after 4 hours of incubation with the OptiMEM and construct complex.

I wanted to ask how can i select for the transfected clones. I will be using confocal microscopy to identify/determine the success of my transfection, but i need to know when should i add my selection media (containing G418) and at what concentration? is there a specific protocol for selection?

if anyone has any idea or previous ex[perience, please let me know, because my lab usually performs transient transfectants and i am the first to attempt formation of stable transfectants.

Thanks in advance

Regards,

Sushi

Thanks.
can you tell me whether in the meantime, i can split the cells and keep monitoring their growth in different plates, right?
how long does the selection process usually take? is it only as simple as adding G418 after observation, or are any other steps required?

Thanks to anyone who might give me the answers.