Notes:

Is it true?
How do we generally judge if we think something is true?
(let alone the philosophical discussion about whether something at all may be ever said to be true - everything is relative, changing, etc)

But in daily life one has make decisions continuously whether one regards something as true: e.g. judging if something you see is real; when asking route directions, etc.
So how do you decide whether you think something is true?

Probably you use one or more of the following 'methods':

• you've experienced it yourself
• you judge plausibility based on your previous experiences/knowledge
• you trust source/ expert
• you estimate the frequency: how many people say it? Seems superficial, but in fact you use/combine judgements of many people. Democracy is based on it, peer review