You really don't need to check everyday if you are lookig for your 3 day window, you only need 2 readings, 3 days apart and you don't even need to begin doing that til 10 days after your yeast pitch.
And if you are opting for a long primary like the month long one many of us do, skipping secondary altogether, you really don't need to take any, though I generally take 2, one on yeast pitching day, and one on bottling day.
That's my average hydrometer usage for normal beers. If I secondaried, I would wait tile day 12 and take a reading then again on day 14, but often I will just take one on day 14 and if it is my target gravity range that my recipe states, then I am fine with one reading and rack it.
And as to how....and how much. You take as much as you need to fill your sample vessel which is just a few ounces, which you drink after.
Like my snazzy new avatar? Get Sons of Zymurgy swag, here, and brew with the best.
Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman
I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew