The phoneme /m/ is produced exactly in the same way in English and Spanish, so it doesn’t pose any kind of trouble to Spanish speakers.
Spelling: m (meat, move), mm (summer, common), mb (climb, dumb), mn (condemn, column)
Do the sound /m/ in the same way you do it in Spanish. For once, it’s a very easy task. It may be interesting to have a look at the spelling, though.
Remember that when the m is doubled (summer, common) the sound doesn’t change.
Have a look at this interesting example:
The meaning is different (1. deep unconscious state; 2. punctuation mark) and the preceding o is pronounced differently as well, but the /m/ sound remains the same.
Also keep in mind that the consonants b and n become silent when they are placed after an m at the end of words. So you just have to say an /m/.
Now, listen to some native speakers pronouncing the /m/.