Dahlias

Hi All

i have got some great advice from you all, so i need some help with my Dahlias

I grew them from tubers in pots over the summer, as i did not know what to do with them, they have grown very tall and not very bushy.  as summer comes to end, my dahlias are still flowering

so my questions are as follows:

• what do I do with the plant once it has stopped flowering?
• do I cut the main stalk back? how?
• people talk about lifting them over the winter, but as mine are in pots, should I put the pots in the shed over the winter?
• when spring comes what do i do with them then?

thanks in advance