Before you sit down to write your own song, you should become familiar with the R&B style of music. Listen to the radio, buy records or CDs, download old Motown and R&B songs, or even study up on the history of R&B. To know how to write songs that fit well with this type of music, it is best to have a thorough understanding of established songs as inspiration.
Once you are familiar with a library of R&B music, the elements of an R&B song will start to reveal themselves. Understand the components of an R&B song. These are the "hook" or chorus, the verses, intro and extro. Often, R&B songs will also feature a breakdown, where the music will vary in style or pace in order to make a certain lyric or point take emphasis. A useful activity would be to change the words of an existing song, just so you can become familiar with the structure. Once you know the parts of a good R&B song, you will have a better understanding of how to write one of your own.
When it comes to writing song lyrics, the subject matter is what will most often draw listeners in, along with the beat. In order to touch people with your lyrics, write honestly about subject matter that is close to your heart. The prevailing theme in contemporary R&B songs is certainly passion, whether flames are being ignited or snuffed out. Writing a song that deals with this topic is perhaps the safest way to make your song fit within this genre. The more honest and emotional your song is, the easier it will be to write and the more impact it will have on the listener.
Draw inspiration wherever you can, then start writing and developing your song as it goes along. The simplest occurrence can trigger a song, whether it's a few rhyming words, a sound you hear or an emotion you feel. It will most likely take several revision processes before you can complete a song that you consider strong. Often the beat comes first, while other times lyrics can be the inspiration for the musical composition. A strong bass line is commonly a backbone in R&B music, so getting that down first may inspire the rest of the song.