I'm sure that I'm in the minority but I tend to use my Retinues to shore-up any gaps in my army. For instance I'm often lacking in archers because I hate Light Infantry with a passion (a hold-over from CK1). So I use shock/skirmish retinues a lot. Usually in a 1:1 ratio. Then I add some calvary retinues when able-usually in a 3:3:1 ratio with cav being the 1. When using the retinue alone I put all the Calvary in on one flank with a cav/flanker leader and the bulk of my forces in the center with a good leader- Heavy infantry leader/inspiring/unyielding leader which wins most battles for me even against greater numbers.
When using my retinues with the regular army I try to hit the 'trigger' points for tactics I want and of course avoid trigger points for ones I don't want. In the end I think your commanders are more important than army composition-the right leader in the right place can win battles that on paper he should lose horribly.
As a side note, I've read that LI are better in CK2 but I just don't trust a guy wielding a club or a butcher knife to be the backbone of my army (this is how I envision light infantry except for vikings).
When using my retinues with the regular army I try to hit the 'trigger' points for tactics I want and of course avoid trigger points for ones I don't want. In the end I think your commanders are more important than army composition-the right leader in the right place can win battles that on paper he should lose horribly.
As a side note, I've read that LI are better in CK2 but I just don't trust a guy wielding a club or a butcher knife to be the backbone of my army (this is how I envision light infantry except for vikings).