In Snow Leopard when you need to accent letters you can memorize the ones you use most frequently, such as é (hold down the option key, hit the e key which gives you the ´ then hit the e key a second time which places the e under it), but for the rest you have to go to the Special Characters menu item (Edit > Special Characters) and search.
In Lion you type the letter you want to accent and continue to hold it down and the character picker appears.
Character Picker in Lion
You mouse click on the accent you want and it is added. You can also click the number key that appears under each choice rather than mouse key to get the same results.
This will save you time.
Beginners Mac Blog 