Because it grows so fast, you can often save a day by using TG1 rather than a less healthy strain. Try looking at the plates against black and white backgrounds to help see the color when it is just starting to develop. Bluescript SK and pUC vectors give good color development. Bluescript KS takes much longer to develop the blue color, so don't use this vector unless you have to. At 14 hours, the blue color is just barely visible.
Colonies take longer to grow up embedded in top agar than on an ordinary plate.
Some colonies will burst up to the surface and become much larger than the others. My new method, adapted from Ewa Davison. Let the plate sit at least one hour to allow the liquid to absorb into the agar. Then plate the transformation mix as per usual. Commentary A. Don't be a wimp about multi-step constructs.