I have posted this a few times recently so I'll just copy/paste my post
Recall is sooo important. I practice with Jackson a few times a week still at 3yrs old -- I went and bought a light 50 foot line, let him go out exploring, and use "here" or "Jackson, here" as our command and always treat him. I also randomly give him a treat if he chooses by himself to come up to me, or walks near me, or checks in, etc.
You can also begin when in the house or in a secure fenced in area. Sit on the ground with her as if you are doing a training session. Reach over her head, grab hold of her harness, let go, and treat. De-sensitize her to the motion of your hand reaching for her so she does not run.
In the beginning stages, NEVER say "come" or "here" or whatever your command is and then immediately pick her up and bring her away from the fun. Let her come to you, get a treat, and then go run off again. If they learn coming when called always = something unpleasant (such as a bath, leaving a fun place, getting brushed, etc) they will learn to ignore it. I notice a lot of people don't even realize they are doing it: "Rover, come here" *grabs for bath* "Come on, Rover" *starts cutting nails*, LOL. you get the gist. Always make your command word a positive one.
Also, don't over-use the phrase. A lot of people will say "Come!... come. Come! come come come!" Dogs don't understand English in the way we do obviously. And "comecomecomecomecome!" means something completely different than just "come". Set them up for success! - try not to let them fail. Try only saying your command when you KNOW they are going to come, in the beginning, so that the word doesn't become useless.
In an emergency situation, you could always get down on the ground yourself. Usually dogs will think you found something interesting and come over to check you out (as we are not usually on the ground on their level).
Check out YouTube channel
zakgeorge21 and
kikopup for two really informative training channels.