What is the best way to get some Lisk? Should I wait for exchanges?
At the moment, IOU tokens of Lisk are being traded on Yobit, Chameleon Bit and Bloombit. It's a risky movement.
C-CEX and others, I suppose, will add at the launch (May, 24)...
Hopefully Polo will add at launch too.
Welcome to the board!

About the best way to get it, it's hard to say, but buy on dumps. If you don't see deep variations, consider this useful recommendation from LiskQH...
I missed the ICO

is it a good idea to buy lisk at launch or will it be too high then?
Maybe it's better to buy over the course of a few weeks. Every day a small chunk.