Like with most things it's just a matter of practice and knowing what to look out for. Same as with birds or leaves or whatever. Firstly, is it serif, sans-ser

Like with most things it's just a matter of practice and knowing what to look out for. Same as with birds or leaves or whatever. Firstly, is it serif, sans-serif, handwritten, monospaced etc? This will narrow it down, but distinguishing between similar fonts, such as Arial/Helvetica, Avenir/Futura, Garamond/Caslon etc. requires looking at individual characters. Lots of characters don't change much between typefaces and can be hard to identify at small sizes, but others can change a lot so they're the ones to look out for - including the lowercase g, uppercase Q and ampersand &. Is the g double storey or single storey? Open Sans and Noto are identical except for the g (Open Sans is double storey). What's the tail on the Q like? Does it cross the circle, is it curved or straight? Open Sans and Droid Sans are identical except that the tail of the Q is curved in Droid Sans and straight in Open Sans. (Also the uppercase I has bars in Droid Sans). Arial and Helvetica can be told apart by looking at the lowercase t. Arial's t terminal is at and angle whereas Helvetica's is horizontal. Also the terminals of the uppercase S are at an angle whereas Helvetica's is horizontal.