Personally, I like a few mixed to get the feel of ball on bat and get the hands going, followed by working on a few key shots to make sure I'm playing them right. Main aim is to cut out errors early on by making sure I'm playing straight through the ball and moving my weight back and forward well. Ideally after the throwdowns I want to feel comfortable with what I'm doing and ready to concentrate on the match/bowlers I'm facing rather than my own technique.
I'm quite bottom handed, so some off-side drives focusing on getting in position and hitting the ball down, some full and straight focusing on playing straight through towards mid-on/midwicket rather than playing across the line which I can do early on, and then a few short to pull (probably my favourite shot) so that I'm playing something off the back foot too, focusing on hitting it down and hard without slogging, and also because it feels good to whack a few short ones before you go in!
Of course that's all an ideal and more normally I end up clumping a few full tosses straight back at someone while wishing we had permanent nets at our ground...