Which following would you consider to determine if the source has any bias

You will have to look at whether or not the creator of the source had a really positive or negative outlook on the situation.

If they are -for example- great friends with a bully, they will not tell as much of the truth, but if they are enemies, they may tell a very exaggerated truth to get them in trouble.

You must look for a very neutral feeling on both sides of the matter. If the author has an opinion, more likely than not it will affect the way they share the information

consider an orange peel: if you want to try and lay it flat, you have to stretch it, we know exactly how things are being stretched or squashed at any given point. we have many different map projections because each has different patterns of some projections can even preserve certain features of the earth without