How do you design the personalities of your main cast to have good dynamics with eachother?

Yeah, I like that setup a lot, and I usually use it to make the groundwork for my characters. The list I made is just an extension of that that I found myself falling into the pattern of.

 

If you have a band depending on your story type they may all share the same goal. This goal could be Kill the evil dragon.
But give them all a different motivation. One want to kill the dragon to clear the family name as his great-grandfather failed to kill the dragon and it destroyed his town. Another has a revenge agenda against the dragon, another wants to reward the head of the town offered and so on.
You can often make a personality from their motivations.

But I don't sit a focus on making them all "work" because sometimes it can be more interesting if they don't but learn eventually to work together for a common goal. What I do make sure I do if have plenty of colour. So I don't have two character that are basically copies of each other, or the one pointless character that offers nothing to the group. I do try avoid labels like 'the funny man' and 'the straight man' 'the know-it all' because that confines the characters to a type.

Sometimes it's fun to use those tropes and then play with them and stick a square peg in a round hole. So make the girl the funny one and the young one the smart one and the old guy the Idiot. Or make the girl the leader.