What beers are good for making shandy? If I'm looking for a beer to make shandy with, what should I be looking for, in terms of flavour?
It seems as though lighter beers are the most popular:


In northern Germany, a half-and-half made of Pilsner beer and lemon soda is known as an Alster
In southern Germany, a mix of Weißbier and lemon soda is called a "Russ'" (Russian).
The Radler (cyclist) Biermischgetränk has a long history in German-speaking regions. It consists of a 80:20 or 70:30 mixture of beer and German-style lemonade (not American-style lemonade, but sparkling lemon soda, similar but not identical to Sprite or 7 Up).


From wikipedia

In general, shandies are meant to be "refreshing" drinks, so the lighter beers makes sense.  You can get creative with dark or hoppy beers, but in general you want lighter brews like pilsners, saisons, golden ales, etc.