Buddhism and Stereotyping Perceptions An answer has prodded me to completely reconsider my understanding of Buddhism and emptiness [this answer]. I never realized that Buddhism involves the dismantling of preconceptions and false certainty. Due to some spiritual experiences, I feel it's clear that the path to a happier life for me is changing this. 

However, I know for a fact that I continuously generate such preconceptions and approximations almost pathologically. I feel that doubt greatly arises from this, in my mind; I keep making inexact and hasty conclusions, and assuming things. I cannot merely not know. 

My question is: What are the ways to dismantle such biases of mind? I specifically mean those of speculation, stereotyping, jumping to conclusions, and so on.

Simply put, I'm wondering how one trains or comes to accept uncertainty.
The habit of mind to Speculate and Stereotype is developed over thousand of years of psychological evolution. It was at some point in history, very important for humans to classify the objects, they saw and and hence speculation and stereotyping gave advantage, when the world around humans was not very complex. 

The point I am making is, these are habit patterns of mind created over thousands of past lives. 

As against 'jumping to conclusions', as we mean it in a judgemental sense, is some kind of recent phenomena of fast paced life. 

May be, even the stone age humans must have been jumping to conclusions at sight of some thing akin to snake.

So, I am trying to say, these are habit patterns of everybodies mind.

Now answering your question, how one trains to accept the uncertainity

The point of Buddhism is not to train the mind (there are therepies in modern psychology to do just that), instead we try our best to see things as they are. So the way to dismantle the bias is, to be aware to the present moment and be watchful of your mind as much as possible.

This gives rise to intelligence, and through that intelligence you dismantle the habit pattern.

When you fail, don't be judgemental towards yourself and feel bad. Instead make a note and understand that as all your intelligence was available what you did was the best you can do.

Through such repeated feedback your biases will be dismantled without specifically trying to train the mind which is a superficial and phony solution.

To put it simply, Stay Aware to the Present Moment.