Usually in hip hop and r&b, the second and fourth beat will be a snare or clap. So the most simple example would be song "The Way I Are", where is: kick-clap-kick-clap, and that's 4 beats. U count that for one minute and u get BPM (beats per minute) of the song. Sometimes it's not that simple, and then goes like kick kick-snare-kick kick-snare. But always remember, the second and fourth beat is almost always snare or clap