When you critique someone’s work, give them the happy sandwich. In other words:
The bread:
1. I liked this part, this was great, and such-and-such was fabulous.
The Meat:
2. The so-and-so needs work, I didn’t quite get this part and I think when the hoo-ha gets less complicated the plot will be better.
The bread again:
3. Overall, the thingamajig made the story believable, and the other thingy was really funny.
Or whatever. You get the idea. Include the good stuff, but give the real critique, too, not just making up something for the moment. It’s hard to critique someone’s work, but if you give them the Happy Sandwich, it’s a lot easier to hear it – and to give it.