Hey CJ,
listen to Bob Marley, there's a lot of melodic ideas in his
songs. sometimes I set up a cool bass line first and then try to sing some words to it. what I found out is that too many notes or melodies spoil a song, and that simple tunes are more catchy... try to experiment with scales too (for Reggae I often use pentatonic but also myxolydic!). I often find good melodies when just singing to one single chorus (you know Beck's "Loser"? one chord is enough for the whole chorus, but it's extremely catchy!)
imagine you're sitting on a Jamaican beach and start jamming! ;-)
cu, smirky