DONENESS TESTS

When a recipe says to 'bake until done', that sounds like a specific instruction, but in reality you must learn what constitutes 'doneness', and use your own judgment. To one person, a bread that is dark golden brown and very crisp is 'done'. To another, light gold is the correct color, with a more moist interior. Whatever your personal preference, there are standard doneness tests you must learn before you can begin experimenting. First of all, always begin checking your cakes, cookies, or breads at the earlier doneness time specified in the recipe. In fact, I like to set my timer a few minutes earlier than the shortest baking time called for. You can always bake longer, but overbaked or burnt products are ruined!

Cakes

* A toothpick inserted in the center of the cake will come out either clean or with only a few crumbs clinging to it. If there is uncooked batter or many damp crumbs on the toothpick, return the cake to the oven and continue baking. Remember to set the timer again! I usually check after 3-4 minutes if the cake isn't quite done when I first test it.
* When a cake is done, the edges will begin to pull away from the sides of the pan. This is an indication that the internal cake structure is firm and will hold after the cake is removed from the oven.
* Usually cakes are baked until they are an even golden brown color over the entire surface. The edges can be slightly darker.
* Using your index finger, touch the cake lightly in the center. If the cake feels springy and the indentation fills up when you remove your finger, the cake is done.

Quick Breads

* Breads should be golden in color, slightly darker around the edges.
* A large crack running down the center of the bread is normal. The inside of the crack should not look wet.
* The edges will begin to pull away from the sides of the pan.
* You can use the toothpick test for quick bread doneness too.

Cookies

* Cookies should be evenly golden in color.
* Cookies usually cool on a baking sheet for 1-2 minutes before removing. The residual heat from the cookie sheet will continue baking the cookies, so if the cookies don't look quite done in the center, they will finish baking in this short time.
* When cookies look done, they are done. You can use the fingertip test, but you'll usually be able to tell they are done just by looking at them. Make sure to follow the doneness instructions in the recipe. Brownies, for instance, are usually considered done when you 'observe a dry, shiny crust'.

Yeast Breads

* The crust should be an even golden color.
* The bread will pull away from the sides of the pan.
* The bread will sound hollow when you tap it lightly

Source : http://busycooks.about.com