Your question is too general. A lot depends on what decision you are making and which beliefs are influencing it. A decision has to be guided by some beliefs, otherwise it would just be random, and that can't even be called a decision. — SophistiCat

I agree with you on the fact that decision can't be made without beliefs but if you read the title then you will know that I'm not saying that we have to make decisions without any beliefs I'm talking about personal beliefs. Yes we have to use some beliefs and those can even be personal but the rate of success for a decision made by an average man according to his personal beliefs is very low mathematically. I'm basically saying that for a normal person the best option is to not make decisions according to his personal beliefs but he should see the things from neutral point of view (get the information or beliefs from surroundings and verify those) and then he will have higher chances of making a good decision mathematically. But being neutral is in itself a paradox because you still have to somehow verify the information and there will be a influence of personal beliefs even if a bit.

You seem to be using "belief" to refer to (moral? religious?) value judgements. But obviously some value judgements are always required when making any decision, so you must be referring to some specific kind of belief? — Echarmion

We are talking about beliefs in general whether moral, religious or any other beliefs. Yes we need a belief to make decisions and practically one can't make a decision without the influence of his personal beliefs he will be influenced by his personal beliefs even if a little bit. We need to have some beliefs for our decision and if I'm talking about a neutral decision then we don't take those beliefs from ourselves but we take them from our environment after verifying those.
Hope that your confusion is clear if not then please do inform me.

What metric are you using here to assess how "good" a decision is? — Echarmion

Well there is no metric for measuring if a belief is correct or not and that is the reason why being neutral while making a decision is important because only 1 belief or a few beliefs regarding a certain topic can be correct and most beliefs are wrong and that's why mathematically being neutral and making decisions without showing baisenes towards your own beliefs is the best option in most of the cases