Usually you'll see a pinkish belly, then the dulling of their colors and those telltale blue eyes...after a few days of this the snake will appear to have gone back to normal. About 48 hours or so after that...you should find a shed...whole cycle takes about a week give or take. Just check the snake afterwards to make sure all the old skin is off especially the eyecaps and the tail tip.
If there is retained eyecaps or retained shed you can soak the snake and then let it slither through a warmish, wet face cloth to help the rest slip off. To soak just put the snake into a small margarine container with just enough tepid water to come partway up the snake's body but not enough that it has to swim at all. Pop the lid on the container, put the whole thing, container and snake back into the tank on the warm side and leave for an hour. Remove snake, let it slither through the facecloth and most of the time whatever was stuck comes off pretty easily. Some people like to put a facecloth in the margarine container with the water and the snake to help it rub against while soaking.
~~Jo~~