If you try to read sentences quickly and loudly, you'll get a better understanding of how the pronunciation works. You probably know more about this than I do, since you speak English and Spanish.
However, you'll find yourself tripping over your tongue sometimes. My pronunciation is not very good, but it helped me to know that some common words can be glided over to help the flow of a sentence:
यह -> yeh
वह -> vo (or 'wo' or 'vwo')
नहीं -> nay (with nasalization)
ज़यादा -> zaada
बहुत -> almost like English "bought" but with more air
है -> heh
में -> meh
(If I'm wrong, hopefully I'll be corrected.)
If you try to read a romanization of devanagri, the pronunciation will often be unclear. Try to get good at reading the devanagri. Remember that अ and आ are drastically different sounds. Remember that झ is different from the J in Jean (which is the sound I always wanted to give it).
For nasalization, do not overdo the trailing N/M that is sometimes transcribed. It is easier to add more of it later than to rid yourself of an overdone N/M sound.
Some words have Perso-Arabic phonemes that are not always pronounced throughout India. I recommend learning some of the Urdu pronunciations, because for some reason it makes it easier for me to say them. For instance, when saying क़ in क़लम (qalam - pen), make a "column" (get the pun? ack) of air with your throat. My suspicion is that a French speaker has an easier time learning throaty sounds than an English speaker.
Well, that's about all of my rambling on it for the moment.