In the area of language phonetics (i.e. what consonant and vowel sounds exist in a particular language), Wikipedia has become useful and maybe accurate enough for beginners. There can certainly be errors, but that’s true for any source of information. When I consider which language to dabble in next–or when I actually start dabbling–I turn to Wikipedia first. I used to go to About World Languages (AWL), but that website seemed to have been hacked a couple of years ago, so I stopped using it. I checked it again just now and it seems to be working.
Look up a language on either website and scroll down to the “Phonology” (in Wikipedia) or “Sound system” (in AWL) section of the article. If there is no such section, you might have to look for another article. For example, I looked in Wikipedia for “Hindi language” and found an article, but it didn’t include a Phonology section. So I looked up “Hindustani language” and found a Phonology section there. Actually, it was just a link to another article called “Hindustani phonology.”
Once you find that section, you should see two tables: one for consonants and one for vowels. They are arranged by the area of the mouth where your tongue is most prominent (relatively speaking). For example, you move your tongue forward (toward your teeth) to pronounce /i/ (as in sing) and back (away from the teeth) to pronounce /u/ (as in rule). Likewise, you move your tongue forward to pronounce /d/ but back to pronounce /g/.
However, the column and row headings of the table use linguistic jargon. If you’ve studied phonetics or phonology before, you probably find that terminology helpful. If not, it won’t help you at all. (Phonetics studies the sounds themselves, and phonology studies the relationship between those sounds. For example, phonetics teaches how you move your mouth to pronounce an “n” in English, while phonology shows that “n” is usually pronounced “ng” before a “k” in English–as in the word “think.” Phonology courses might teach phonetics also, or might require phonetics as a prerequisite.)
If you are an aspiring polyglot, I recommend you take the time sooner or later to learn phonetics and phonology. You can start with something simple such as a YouTube video series or a “Dummies” book. Likewise, the International Phonetic Alphabet (IPA) could be a useful tool for you sometimes. The IPA uses one letter of the alphabet (or even a “made-up” letter) to represent each possible sound that the mouth, nasal cavity, and throat can make, since practically all known sounds exist in one language or another. The letter “r,” for instance, is pronounced differently in different languages, so the IPA uses a different letter to represent each of those “r” sounds. Phonetics and phonology can be very dry subjects, but are a good time investment. On the other hand, if you only want to learn one or two foreign languages, you can easily get by without learning phonetics, phonology, or the IPA.
I studied these subjects years ago while earning my TESL (Teaching English as a Second Language) certificate at Portland State University. Lately, I’ve had to relearn them and expand my knowledge beyond the basics, in order to use Wikipedia for this purpose. Here’s how: If the column or row header includes a word you don’t know or don’t remember (such as “alveolar” or “fricative”) and you can’t figure its meaning out for yourself, just click on the word you don’t know. Chances are that it has been made into a link that will take you to another page that explains its meaning. (A link in AWL will take you to a Wikipedia article.) Sometimes, the IPA symbol inside the table is a live link to an explanation of the sound.
If not, you can combine the column and row header for the sound, type that phrase in, and look it up–for example, “voiceless labial fricative” (known as /f/ as in fish). You can even type the words out of order. Type them in the Wikipedia search box and it will describe the sound and how it’s made. Try to figure out what you can and ignore the parts that make no sense to you. Then click the audio link on the right side of the article to hear it pronounced. Listen to it many times and repeat after it a few times, until you figure out how to approximate the sound yourself. Voila: You can now pronounce it well enough to get started.
Eventually, I recommend having your pronunciation checked by a native speaker or a tutor of that language who has studied phonology or linguistics or who specializes in teaching pronunciation or accent reduction. If necessary, schedule additional sessions to improve your pronunciation, if you want to speak it well and be understood by most native speakers in conversation.
This Wikipedia approach is what I take. I did this for Vietnamese when I dabbled in it last year (but haven’t had my pronunciation checked yet). The b, d, and g letters are pronounced differently in Vietnamese than in any other language I’d studied.