Learning to write lyrics can be the hardest or easiest part of writing songs for different people. I myself am a more music-oriented person and therefore preach by writing music THEN lyrics. Most composers preach this order, but let’s not get ahead of ourselves.
As I mentioned in the opening, I recommend that you focus on the music and not the lyrics. I recommend this because it makes writing lyrics much easier for a couple of reasons.
First of all, the creation of your music gives you a precise idea of the kind of rhythmic spacing you might be working with. You will know that if you have a melodic vocal line for the chorus that is composed of 5 syllables per line, you know what kind of lyrical lines you can include there. Once you have it, you can try one line and once you have nailed it, you can also nail your rhyme structure and pattern.
Secondly, I have found that a great melodic line makes writing lyrics ridiculously easy. When you have a great melodic vocal hook that is memorable and that you’re excited about, then you’ll find yourself singing dozens and hundreds of possible lyrical phrases for that line. You’ll see that being prolific is second nature when it comes to writing quality lyrics when you have a great melodic line to which you can keep throwing lyrics.
When this happens to me, I’ll write dozens of lines that fit there and although you’re only going to use them and you’ll have room for a handful of them, those extra lyrics are right there in your lyric book (another important point in how you write lyrics is that you should have a lyric book to house all your ideas) so that you can get them out when you find yourself stuck in another song.
Spacing and rhyming structures may not fit perfectly when importing lyrics into a different song, but you can adapt them. The point is that you’ll get quality ideas/lyrics that will probably be of higher quality than a line you’re trying to write for another song later.