I have seperate dishes and utensils for milk and meat but when I am done eating I usually place the dirty dishes in the sink although I never keep meat dishes in the sink at the same time dairy dishes are there. I just read the koshering a kitchen section on the webpage and see that I should not keep dishes or utensils in my sink. What should I do with my dishes and utensils? Are they not kosher anymore?

You should have two separate sinks for both meat and milk. If you have two but did not separate the sinks – you should kosher them by pouring boiling water on all the surface of the sink and designate one milk and one meat. If you have only one sink you should use a plastic tubs to fit the sink, or have two racks to place the dishes on – one for meat and one for milk. The dishes are still kosher unless you used both dirty dishes together with very hot water in the same sink.