I start by looking at the structure and trying to work out what sort of thing I am looking for. People and places are quite easy to spot by the structure. Otherwise it's a thing or event or concept which is harder to narrow down. If there are lots of very small letters, it is likely to be maths or science as they are likely to be formulae.
Very occasionally, there will be an odd combination of small words that give a clue. Lots of people (not me!) got Meryl Streep quickly as they spotted Out of [redacted] appearing and immediately jumped to Out of Africa. Today, I got the broad area on my first guess due to an unusual indefinite article in the first paragraph, although DH had other thoughts on it and didn't jump to the same conclusion that I did.
For people, he/she narrows down the sex. I then try to narrow down their area of fame with words like wrote/performed/discovered/invented.
Places often contain located. Then words like country, city, river, mountain. Africa/Asia/etc to narrow down continent. North/south/east/west can help but usually only if they appear in the first paragraph.
Maths/science ones it's useful to put in single numbers and letters. For maths particularly, n and x as they frequently appear in formulae. Chemistry related, letters like C,N,O,H etc. For monosaccharide the other day, I typed in the whole alphabet 1 by 1. Species is a good one to identify if it is plant/animal.
Personally I like Roman/Greek/India/China as they tend to narrow down the history part. I also like to put in a selection of materials - wood/metal/plastic/cloth etc as it can often narrow down what a thing is made of, although nothing I tried helped with rope!
I'll stop now or I could witter on all day about what I would try for different categories!