Um... focus - I pretty much use my whole body to cue. I don't know if you're familiar with Parelli(his old stuff - new seems to have changed quite a bit so not sure if this is what he now preaches), but that is the way I started out many moons ago(got into Parelli pretty fanatically about 20 years ago
) and one of the tactics I still find invaluable.
*When I started learning this I had also started learning behavioural psych & c/t & some was contradictory to the other, but I stuck with the PNH principle of starting with the 'smallest' cue & escalating as/if needed until I got a response. Ie. starting with the cue I ultimately want my horse responding to.
So... I'm just sitting on my horse relaxed & decide I want to go in a certain direction. So first thing is I raise my energy/body to tell the horse I want to do something
(get the horse 'at attention'), and then direct my focus to where I want to go. This is where I think it helps YOU to have a target in mind - a particular tree, post of the arena, rock, whatever, so you've got a definite focus.
If/when the horse doesn't understand to 'listen' to that, then you 'point' your whole body towards that point, which inevitably includes your legs(I use direct leg aids, of which the horse already understands before I get on). If/when the horse doesn't understand how to listen to that, then you add rein cues & stronger legs.
After a while, the horse learns to do 'what comes first' without waiting for 'stronger' cues.
Once he's learned reasonably solidly to 'follow my feel' then I start working on sustaining it - asking him for something, then relaxing & 'expecting' him to keep going in the manner I asked. I do this by using no pressure/energy except when I need to 'correct' him for slowing, turning, whatever. Of course, along with the -R you need to start that in 'baby steps' too & +R for little 'wins' to begin with, asking for gradually more as he 'gets' it.