The Basics[]
A Travel Agent doesn't travel on your behalf - they allow you to travel.
Equally, a Reducing Agent isn't reduced - it reduces some other substance.
O.I.L.R.I.G reminds us that Reduction Is Gain of electrons.
Warning...this explanation may affect your mental balance but you don't actually have to answer exam questions in these terms (see below)
If a reducing agent allows a substance to be reduced then it must be providing the electrons that substance needs.
In other words, the Reducing Agent must be losing electrons of its own.
And, O.I.L.R.I.G reminds us that Oxidation Is Loss of electrons.
So, while a reducing agent is busily reducing something it is simultaneously being oxidised.
Obviously, it is easier to spot a reducing agent by looking for the substance that's been oxidised than trying to work out electron-transfers in an equation because full equations never contain electrons.
Exam Hint[]
You won't need to explain the above on an exam. You may need to explain how you can tell which substance is the Reducing Agent by looking at their Oxidation Numbers.
If you don't know the rules for working out Oxidation Numbers press here.
It's all about electron-transfer but oxidation numbers are an easier way to spot reducing agents.
You should know that a substance being Oxidised increases its Oxidation Number.
So to find the Reducing Agent in an equation you only need to find the substance containing an element which has had its Oxidation Number increased.
You may then have to explain your choice in terms of electrons.
If so, you can still use O.I.L.R.I.G. as at GCSE but it would still be easier to spot the Reducing Agent by Oxidation Number.