How do I know when sweetcorn (and tomatoes) are ready?

[geogteach]

Sweetcorn just not really sure when to pick.
The tomatoes i'll admit have not been greatly cared for but there are a fair few there they are just all green, I assume thats down to lack of sun, do I just leave them and hope or bring them in to ripen on the window sill?
While i'm at it I also have a pumkin when do I pick that and can I then store it for halloween?

[mustrunmore]

Sweetcorn... the fluffy bit at the tip is brown.
Tomatoes... should be red, but we always cave in, pick early, and try to ripen on the window sill.
Never grown a pumpkin in my life.