The whole point of a song is to get a meaning across and this happens with the music and the text. Do you know what you are singing about? If the song is in a foreign language make sure you know exactly what the text means as well as working on the correct pronunciation. There are numerous YouTube videos covering the pronunciation of most of the well known opera choruses.
If the text is a bit vague then discuss with others what they think the text means or just decide for yourself. If you are still unsure then make something up. You have to have an intention in mind in order to get the song over otherwise it is just a beautiful sound without any meaning and after all the audience want to feel a connection with you and this comes through your interpretation of the text. The intention of the text will create your sound. Most pop songs and musical theatre songs do have a clear meaning to them however some songs are based upon poems which can make it unclear what the poet meant. The most important thing is that you have an understanding of what the point of the text is. Older songs sometimes use unfamiliar language, the meaning at the point of writing can even be different to our understanding of those words. Some words no longer exist.
The text must be clear as a whole and each word clearly understood. I have been to many a performance where arias are sung in English so that the audience can understand, only for the text to be so unclear that nothing is understood. Singing in English may seem easy but in practice it is the hardest as it is our most used language and as such we articulate less clearly. Even when people are just speaking they are sometimes hard to understand and require effort on the listener’s part. The audience must be able to relax, enjoy and be swept away with the song. It is not up to them to put in any effort, it is the performers job.
The rhythm of the text is important and you can practice speaking the text to the correct rhythm before you sing it. Especially fast passages benefit from this approach. Then sing the phrase on one note and make sure all your words are clear and then sing the melody on a vowel only and once you feel confident with this put it all together slowly and then work up to the speed required. Keeping in time is very important so consider where you might be tripping over the words so that they slow the whole down.
Exercise
When you are just speaking see how clearly you can enunciate your words, it might come across as odd but for singing this is just what is needed.
