Counting syllables is all about the way we speak. If you can speak English and you have no problem being understood, you are using syllables every time you open your mouth. You just have to realize what they ARE, and then there should be no reason to fear "knowing' how many are in your lines of poetry.
Here is the dictionary definition of a syllable: an uninterrupted segment of speech consisting of a vowel sound, a diphthong, or a syllabic consonant, with or without preceding or following consonant sounds: “Eye,” “sty,” “act,”and “should” are English words of one syllable. “Eyelet,” “stifle,”“enact,” and “shouldn't” are two-syllable words.
Let me break down that definition. Uninterrupted segment of speech means that each time you change the position of your lips and tongue you are moving to a new syllable. Say the word HI to yourself. Add a new word: HI / Mom. You have to change your tongue's position to a new way to say Mom. So you just spoke two syllables. HI, MO/THER. You had to change three times your mouth position, so you added one more syllable, and on and on it goes.
Now to define "consisting of a vowel sound, a diphthong or a syllabic consonant"(I'll get to the "without or without following consonant sounds" later): What is a vowel? Well, you have to distinguish vowel LETTER from vowel SOUND. There are five LETTERS (and six if you include Y, which can function as both vowel sound or consonant sound): A, E, I, O, U. These five letters, by the way, represent most of the DIPHTHONGS of English. Diphthongs are LONG vowel sounds. It means they finish with a W or a Y at the end of them. When we say A, What we are actually saying is EY. You could actually keep your tongue really high at the roof of your mouth and keep it there on the Y part, just to exaggerate it (Y sounding like a consonant not the vowel sound). But normally we don't stop EY (A) high in our mouth.
Here is what A, E, I, O, and U look like in the "phonetic alphabet" I use in my ESL classes: EY, IY, AY, OW, UW. Say the sound O to yourself. You are actually rounding your mouth to produce a tiny OW, and if you tried, you could make a W sound at the end of it.Try it. Same with UW. Other Diphthong sounds are OY, as in boy and AU as in TOWN. Notice spelling has nothing to do with sound. Town is not the OW sound like in OWN. It's written in phonetics as AU. We have many ways to spell the same vowel sound in English but there are only a total of 13 actual vowel sounds in American English. British English has a few more, and I don't know how to say them. Also you could include IR, ER and UR as in LEER, LAIR and LURE, respectively. But I like to think of them as simply the vowel sounds IY + R, EY + R and UW + R.
Look at the words Leer, Lair and Lure. How many syllables does each word have? The answer is simply ONE. When I pronounce the word LEER, I do not divide it up in my head and speak like this: LE ER. NO, I just smoothly say it all together. LEER. About the only time we divide up a diphthong is when we use a hypen, as in the word RE-Elect. So how many syllables in Re-elect? I hope you guessed THREE. RE-E-LECT. Where to divide one's syllables is a little more difficult than just speaking them. If you ever need to show syllable division and are not positive of it, just see a dictionary.
The other vowel SOUNDS of English, in addition to the 7 Diphthongs I noted (EY, IY, AY, OW, UW, AW and OY) are the SHORT sounds of English. Most diphthongs have "short versions" of themselves. That means we do not have an exaggerated possible ending of Y or W at the end of the short vowels. The short version of letter A (whose pronunciation sound is written as EY) is E, which is the short E found in SET and PET. The short version of letter E (whose pronunciation is written in phonetics as IY) is I, the sound you see usually represented by I as in PIT or HIT. The short version of Letter I, whose pronunciation is phonetically written as AY, is the AH sound as when we saw AH-HA. But normally the spelling is an O, as in HOT or POT. See how complicated it gets for my students learning the crazy spelling rules of English? OW and OY have no short versions to contrast with; however, AU (which represents the sound in TOWN) is the sound written with the alphabet letters OU, as in FOUND or SOUND, but sometimes as OW as in ClOWN! Its short version is the sound found in PUT or the sound represented by two O's, as in BOOK. But the other double O sound as in SCHOOL is actually the long diphthong sound of UW.
There are two other SHORT vowel sounds of English. They are the SCHWA sound which you make when you say UGH!!! Its phonetic representation is an upside down e. The Schwa sound is the most popular sound of English, because we reduce a lot of our words to it. Example: I'm gonna do it. GONNA is usually pronounced both syllables as a schwa sound. Like saying GUN NU. And finally we have the short sound found in the first syllable of my name AN/dre/a.It's the vowel sound found in both syllables of BATMAN, so I call it the BAT/MAN sound.
All the individual vowel sound components I just listed above are what make up the syllables of English. When they say "a syllabic consonant, with or without preceding or following consonant sounds" that means that you can have more than one consonant sound either in front of or behind the vowel sound. Here are examples of one consonant + one short vowel as a syllable: DO, TO. Here are examples of two consonants + one long vowel sound as a syllable: STY/ CHI. Now here are examples of ONE syllable consisting of a short vowel followed by one consonant: OF/ AT. Here is an example of ONE short vowel sound followed by more than one consonant: OFF/ WITCH/ APT. OK, now to explain how this works. When you say the word APT, do your speak it like ONE smooth flow? YES, you do. You do not break it up and say to people AP T. You just say APT. ONE mouth movement. Think of the word SKIPPED. How many syllables are there? Did you say two? or even three? You are wrong. Did you say ONE? If so, you are correct. Do you go around saying the word like this? I SK IP PED. NO, you don't talk like this. If I wrote it phonetically, it would look something like this: I skipt. It's all in the SOUND that you are reproducing. The ed is the sound of T (in this particular case) and has no vowel sound to it!
Here are examples of more LONG sounds (Diphthong vowel sounds) that either begin or end with consonant sounds: HI/ OAT/ ATE (silent E does not count as anything)/PIE. Here are examples of Diphthongs beginning AND ending with consonants: FEIGN/ HATE/ PEEK/ READ/ FIND/ FIGHT (that one is funny because the GH is silent)/ SHOWN (SH is actually a consonant SOUND, same as CH, not represented as its own single letter in the dictionary).
Finally, here is a rundown of how syllables would look in a sentence, using slashes to show when I stop and begin a new syllable: I/ want/ to/ see/ the/ new/ ba/by/ born/ yes/ter/day/ in/ the/ hos/pi/tal. Do you see how I change to a new syllable every time i go to a new VOWEL sound? Just remember it's not about the number of LETTERS represented. Remember the word SKIPPED. In that word, there is ONLY ONE vowel sound: I. The ED is pronounced as a T. The SK goes together and is not separated when we speak. Other consonant combinations not separated are ones like PHone, SHine, SCribe, PRay, etc. etc. All those words, by the way, are one syllable words.
SOME CONFUSING SYLLABLES POETS
Finally, there are a few DIPHTHONG sounds that are often confusing for poets. We write them as ONE syllable: the ones like OY is one example: OIL, it's ONE syllable, BOY, it's ONE syllable. Another one often confused by people is the sound in FIRE. Here is how to know it is one syllable. Do we pronounce the E in Fire? NO, it's silent. So that does not count. Therefore, The I in fire is the diphthong IR and it is not separated into two syllables. Here is one more example of a confusing word pair: Quite and quiet. If I spelled the first one phonetically, it would look something like this: KWAYT. It's the diphthong sound AY with consonants around it and it is one syllable. HOwever, when I say the word QUIET. I do not pronounce the UIE all together. I make TWO different movements of my mouth and I say KWAY/ET.
Finally, here is my advice. If you really studied it out and did practices on the internet (I KNOW google probably has ESL exercises to practice syllable division) just GOOGLE it and practice, and you will make yourself into a pro. It's all in how you speak. Don't use those unreliable syllable counters. Stand on your own feet and go by SOUNDS.