I recently came across one of these (Remove Fear). How is this used? Can you use it when under the influence of the 'fear' effect (I was under the impression that you could not use items/take actions when affected by fear)?

If not, is it usable on others when they are under the effect of fear?

Thanks - I do not want to waste it by using it incorrectly.

As I understand it, drinking it removes fear from allies in the area under the effect. (similar to a Bless effect)

And you're correct, you can not use it while feared yourself.

I think it also protects you from fear and fear like effects for a turn when you drink it too?

If already feared, you won't be able to use it. Ideally, you should use it before a battle, considering it lasts ten turns. When used, it will protect you and another person/four caster levels (so, basically just you unless the potion is a high-level one) in the area of effect from all fear effects, in addition to removing any current fear effects.

Maybe we can change the description of the potion to read "guards against fear" instead of "removes fear"?

Well, it does remove fear. You can drink it next to an ally who has been feared, and their fear will go away.