Everyone needs to start at the beginning! The biggest mistake made by poets when starting off in structured work is the want to rush in. Admittedly, some are capable but many are not. Regardless, one should always look that the basics first, even if as a refresher.
All sonnets written in English are metered, and the meter is iambic pentameter. Nothing else is acceptable, especially for the traditional sonnets.
For those starting out, there is a simple formula. At first it may appear restrictive, but once this basic form of the meter has been mastered, then and *only then* will a whole new world of variations be open to you.
Iambic Pentameter in its Basic Form
Each line must have exactly ten syllables. The stress pattern must be da-DUM da-DUM da-DUM da-DUM da-DUM.
To practice, you must read your lines out loud stressing every second syllable. You will quickly find that certain words cannot be used at the beginning or end of a line. Although the lines may sound strange when doing this, the stressed syllables should not sound obviously wrong or awkward in their pronunciation.
Once upon a time in a distant land.
This line has ten syllable, let’s break it up into alternating stresses.
once UP | on A | time IN | a DIS | tant LAND
Reading this out loud, we find the word upon incorrectly stressed, it is the second syllable that is stressed, not the first. The remainder are fine stress-wise, perhaps there are stresses on words that we prefer not to be like a and in, but we will address things like that later.
Our conclusion is that this line is not iambic pentameter. It doesn’t sound correct and our tendency would be to stress once. Things like this may be possible later, but *not now.
In times of old, there was a distant land.
Not the most poetic line, but serves the purpose. It too has ten syllables. Now breaking this into the stress pattern:
in TIMES | of OLD | there WAS | a DIS | tant LAND
You will notice something very different here. Apart from the stressing, it sounds and flows very well. For our purpose this will be iambic pentameter.
Bear in mind, this is the most basic form. It is not too complicated, and if you continue to study this meter you will find that it can become very detailed. There are many things to take into account such as different pronunciations of words and the differing stresses. In this type of analysis, we consider only two types; unstressed and stressed. You will find later that many lines are not actually perfect iambic, but they do not violate the overall iambic pentameter nature of the poem.
What you need to do.
Obviously practice writing ten syllable lines with the desired stress. You might decide to use one and two-syllable words to get the idea. Keeps things simple to start with, there is plenty of time for the rest.