Find a non-native speaker of English and get them to read the following words aloud rapidly. Point to words at random rather than in sequence. Score each selected consonant as perfect native accent (1), comprehensible but not fully native (2), non-native pronunciation (3). Note any peculiarities on the right. Do not pay attention to vowels.

Diagnosis
i. any particular phoneme that gives trouble?
ii.any pairs of sound that give trouble? e.g. /p/ vs /b/
iii.any groups of sounds that give trouble? I.e. fricatives /f/, /v/ ... or plosives /t/, /g/, ... or
voiced /b/, /z/, .. or unvoiced /p/, /t/, ... etc
iv.any clusters that give trouble? e.g. /sp/ or /bl/
v. any other points?
Interpretation: Now discuss with the non-native speaker which difficulties are carry-overs from the L1 and which are not.