Identifying fonts is a lot like identifying the model year of a car. Some people seem to instantly know what year that model was made. Others are oblivious.
The key to this is really memory and knowing what to look for.
First there a broad identifiers:
- Serif, Sans Serif, Slab Serif, etc.
Then there are subsets:
- Humanist, monospaced, gothic, etc.
Then there are subtleties:
- The way counters (holes) are aligned to strokes
- The consistency of strokes
- The tails on some glyphs -- i.e. the g, p, q, j, y, etc.
- traditionally unique glyphs -- i.e. the a, z, r, k, (0-9), etc.
It's these factors that help one look at a typeface and identify it. Now, being able to name it relies on the ability to remember that "FontA" has a z which looks like your sample. Or the q in "fontA" never looks like that so that can't be "fontA". It's all memory.
How to use online font identifiers better....
If you need to use a service such as WhatTheFont, it's often best to set up your sample to target these aspects. Remember the online identifiers aren't "reading" the sample. They are scanning the glyphs. You don't need to use readable text as a sample. So copy/paste the key characters into a new document and, if possible, adjust contrast so it is as black and white as possible without degrading the glyphs.
The important thing here is to use minimal text with clear unique characters to assist in the identification. It often takes some set up before the online services can be really useful.
Key characters with contrast boosted.
It can also be very helpful to use as large an image as possible when using the online identifiers. The larger the glyphs the more easily the identifiers can scan them for variances.
Using this sample... one of the suggestions at whatthefont is a variation of DIN which is pretty close. -- See here - So, I would explore DIN to see how closely it matches. My experience tells me DIN is a broad typeface with many faces so determining which "flavor" of DIN it may be specifically will just take visual confirmation.