Question

how do tell what is the reduction reaction and what is the oxidation reaction

Answer 1

by simple rule "Leo" the lion say "Ger"
lose electron oxidation
gain electron reduction

Answer 2

:) thank you

Answer 3

welcome

Answer 4

I like "Oil Rig" or "oxidation is loss of electrons" whilst "reduction is gain of electrons". An example of oxidation is iron rusting it goes from Fe to Fe3+ whilst oxygen in the air becomes O2-.
The oxygen is an oxidizing agent but itself is reduced. Other oxidizing agents include hydrogen peroxide, which can accept electrons from Fe2+ ions for example to make Fe3+. There's more details here:

http://en.wikipedia.org/wiki/Oxidation#Oxidizers