I am facing a big trouble when applying leg aids during trot or canter to increase the speed:

1- Either i lose knee & thigh contact.
or
2- My feet or one of them get out of the stirrup
or
3- I try to keep knee and thigh contact while kicking with my legs, so i find it not strong enough or i am unable to get them far enough to give a strong kick so i just feel it uneffective or like just squeezing.

Please, give me an effective way or the right shape and strength of how to give a leg kick during a trot or canter, is it just inwards or little bit backward or what, and what's the timming to avoid losing balance or missing the harmony with the horse motion?

If there is a video that can show this clearly, it would be great.

Thanks in advance!