Asparagus picking question

This is the third growing season for my asparagus crowns.  I cut three spears today.  It was the most delicious, tender asparagus I have ever eaten.  I did not harvest for the past two seasons to allow the crowns to get well established(or so I have hoped).
 
Now the questions.
What proportion of the spears should I harvest from each crown?
When should I cut them?  Early and let later growth mature or let some early shoots grow and cut later ones?
Will cutting early growth encourage the formation of more shoots?
Will allowing early shoots to grow mean the crowns will not produce as much?
Or, will each crown produce the same number of spears if you cut some or not?

sorry Co-9, I read the title as asparagus PICKLING question.     Can't help with picking~ 
But I'm sure someone can help!  If not here, then google is your friend.  Enjoy them fresh sprouts!
SL

Third year I went pretty light but I have a lot of patience..lol

Say you had 6 spears on one crown I would cut 2

Start cutting then once they are tall enough, cutting them will encourage more to grow

If you have a few coming up at same time from same crown I cut smaller ones and let larger grow up and fern out

You can also cover up a crown and get some white asparagus

I hit them hard with fish/ seaweed/ compost tea when I see the first tips

This has worked well for me you're mileage may vary

Cheers