ok here it goes.
most of us use a 9' leader.
or you can also use a 7' or 7 1/2'
as for the tippet.
most people add around 20" of tippet. some add more to like 36" but 20" is a good place to start.
as you add more tippet to the leader it gets harder to turn the whole thing over, however it makes for a much nicer presentation for finicky fish.

as for the knots.
i use a uni-uni splice, or double surgeons knots.
then for the fly to tippet. i use a uni knot or a double clinch knot.
and if you are going to use a loop knot on the fly, then i use a non slip mono loop.