The four basic pillars of gematria isopsephy which are two

The first adding the letters ordinal value , i.e . the postion of the letters in the alphabet so say the word OGMA would be
  O=17
  G=12
  M=11
  A=16
+_____
  = 56 total
The second is adding the letters in the traditional decimal denary counting system , i.e . going up in ordinals for the first 10 letters then going up in 10s up to one hundred and after 100 going up in hundreds depending on the alphabet size continue thus into the thousands the tens of thousands ect
So In Ogam denary OGMA adds too
  O=80
  G=30
  M=20
  A=70
+_____
= 200 total
These first two methods are valid but they only get you so far and tell you so much

Consider for a minute we take an example from basic english qabalah these words all equal 444
Veil = 444
Evil=444
Live = 444
Vile=444

Obviously the words all have the same letters and so there numerical value is equal but do they match and have much in common is it really vile to live ect maybe for some but I think we are missing something.
All these words have the exact same letters but each word has different letter orders so to get the numerical value that is unique to the word itself we use a method called "the secret whisper" of a word.
This is done by Multiplying the letter order by its high value whether that be the high ordinal or denary.
So say we come back to are name again to show you how its done numbering the letter order on the left side

1 O=80
2 G=30x2=60
3 M=20x3=60
4 A=70x4=280
_____________
          = 480

So 480 is are new total for the denary secret whisper of OGMA and we do the same with the ordinal values

1 O =17
2 G=12x2=24
3 M=11x3=33
4 A=16x4=64
+___________
            =138

Same method but now we have taken into account the order of the letters as well as there values
To help illustrate this we take one of the spellings of the Ogham alphabet OGAM =200 denary

But if we use its secret whisper

1 O=80
2 G=30x2=60
3 A=70x3=210
4 M=20x4=80
+____________
      = 430

So thats the differents between the OGAM alphabet and the god OGMA
Both equal 200 normal denary counting but in secret whisper counting the letter order by its value we have
OGAM = 430
OGMA=480

To recap all four methods.
1. get the ordinal value
2. get the denary decimal High value
3. get the secret whisper ordinal
4. get the secret whisper Denary

These four should be used in every other method you can conceive of.