I have made a decision
"I have made a decision". When I think about this I automatically think, "he hecho un decicion" or "tuve un decicion". But when I looked it up in the translator, it says "tome un decicion". To me this means "I took a decicion"???? I am a little confused!!!
3 Answers
Apparently "take a decision" is primarily British usage, whereas "make a decision" is more common in the US. Although as a general guide I think it is much more common to 'make a decision' in English than it would be to 'take one'
In Spanish however, you "take" a decision, you never "make" one.
Tomar una decisión
The reason being perhaps that you do not generate the choices; the choices are there, available to you and you take your pick. 
Actually I believe that in England a person 'takes a decision' rather than 'makes it' so that is closer to the way you say it in Spanish, you can say 'Tomar una decisión' or even 'come to a decision' which is 'llegar a una decisión'. Sometimes you hear people from another country say something in English which is understandable but sounds a little different and this is an example I think.
I know the verb "decidirse" is to "make up one's mind".
So perhaps "me he decidido".
Perhaps wait until the heavyweights chip in.. 
