Apple has a nice tip up this week on typing letters with non-English accent marks. As they point out you can use the Character Palette, but there's a much easier way that many of us often don't remember to use via the option key. To type an accent you just need to hit an option key combo then the letter that you want to take the accent. So for example, to type an umlaut hit option+u then the u to get ü. To type an acute it's option+e then e to get é; for a grave it's option+` then a to get à. The Apple tip lists all of these handy key combos plus a bunch more.
If you often find yourself typing accented characters you'll end up saving a lot of time by memorizing these combos. And even if you don't remember them exactly, you can probably figure out the one you need if you just experiment with the option key.