How do I use adb grant or adb revoke?

The Android documentation contains the following description of the adb grant and adb revoke commands.

grant <PACKAGE_PERMISSION>

Grant permissions to applications. Only optional permissions the application has declared can be granted.

revoke <PACKAGE_PERMISSION>

Revoke permissions to applications. Only optional permissions the application has declared can be revoked.

Can anybody please give an example of the correct syntax to use them?

I assume that would be a permission like android.permission.WRITE_EXTERNAL_STORAGE, or perhaps just WRITE_EXTERNAL_STORAGE. Well I tried those, and several others and I cannot get it to work.

I also tried (to no avail) several combinations of package and permission, which makes more sense to me (this sounds like a command that would modify a permission on one package, not all)

To Add:

adb shell pm grant com.name.app android.permission.READ_PROFILE

To Remove:

adb shell pm revoke com.name.app android.permission.READ_PROFILE

This changed at the release of Android M, so in Lollipop (at original time of writing answer) you needed to do adb shell first.

adb shell 
pm grant com.name.app android.permission.READ_PROFILE

A full list of permissions can be found here. If you have android build tools set up you can see what permissions the app is using. First use

adb shell pm list packages -f

Then copy the package to you computer:

adb pull /path/to/package/from/previous/step.apk

Then get permissions:

aapt d permissions path/to/app/on/computer.apk

If you happen to not know the name of permission or want to clear all permissions you can use

adb shell pm reset-permissions

WARNING: This will reset run-time permissions for all the apps on your phone. You cannot reset for a specific package.