First choose a simple phrase which you are comfortable to play/ sing.
Eg- S R G M
then do a little more variation
SRGM MGRS
and little more...
SRSR GMGM SRGM SRGM
and more....
SR RG GM MG SRG RGM GM...
and like this move to more & more complex phrases, but keeping in mind to be limited with in the initial notes at least for first couple of phrases.
leter move on and accumulate more notes
Example- SRGM RGRM MGRM RGMM RGMP...and so on