I'm still learning them and I don't get any of it either... But I hope these examples can help ya...
* O2 + H2 ----> H2O
First count the number of oxygen atoms... On the left, there's 2 and on the right, there's 1. So, Put a 2 in front of H2O on the right to have 2 atoms of Oxygen.
* O2 + H2 ----> 2
Now you'll notice that there's 2 atoms of oxygen on both sides. So now we'll move to Hydrogen. There's 2 on the left, and 4 on the right. You'll need to add 2 more to the left side so place a 2 in front of the Hydrogen.
* O2 + 2
H2 ----> 2 H2O
Here's another one:
* Fe + O2 ----> Fe2O3
First, we'll look at Iron (Fe). There is on atom of Iron on the left, and 2 on the right. So, you'll have to place a 2 in front of the Fe on the left, to have 2 atoms of iron on either side.
Fe + O2 ----> Fe2O3
Now since, there are two atoms of Iron (Fe) on each side, we'll move to Oxygen. There are two atoms of oxygen on the left and 3 on the right. Now, you find the LCM, which is 6. So on the left, you'll have a 3 in front of the oxygen (to get 6 atoms) and you'll place a 2 in front of Fe2O3 (also to get 6 atoms of oxygen).
* 2 Fe + 3
O2 ----> 2
Now you'll notice that the number of Iron atoms on the left do not equal the number of Iron atoms on the right. There are 2 on the left, and 4 on the right. Now, instead of a 2 in front of Iron, place a 4.
Fe + 3 O2 ----> 2 Fe2O3
Is this how you wanted it? Sorry if I wasn't of any help... This is how I learned it... In simple words, try to get the same number of every atom on each side.