Reddit mentions of Manuel Pratique (new edition): Vocal Technique

Learn to sight read, and learn basic music theory in general (even a basic music theory class at your local college). Dandelot is a fantastic resource to help sight reading, even though it's in French.

Once you're decent reading music you can try transcribing bass parts (and eventually other instruments) and then analyzing it to see why the part works the way it does.

This won't just help you be a better jazz/classical bassist, it will help you become a better musician.

Practice :) I have this book, albeit it is in french. There is a Spanish version available but I'm not aware of an English one. Not that you need to understand what it written. It is mostly progressive exercises with a very specific technique to recognise the notes. It is very good.
https://www.amazon.com/gp/aw/d/1458420086/ref=mp_s_a_1_2/131-3043784-4441216?ie=UTF8&qid=1502020635&sr=1-2&refinements=p_27%3ADandelot&pi=AC_SX236_SY340_QL65&dpPl=1&dpID=41o2S-V%2BEEL&ref=plSrch

In a nutshell: know master notes on the stave (C, G on the treble key) then know the one immediately below and above. Then the two below and above. Then add more master notes. And practice recognising the intervals (second, third, fourth, fifth).

When I started sight reading, we had this book:

https://www.amazon.com/MANUEL-PRACTIQUE-NEW-PRACTICAL-MANUAL/dp/1458420086/ref=sr_1_1?ie=UTF8

​

I tried to find a version in english but it seems that it's hard to find (mine is in spanish). Really good book, though. You start with a couple of notes as reference and it teaches you from there.