Preferred method for viewing code generated by Template Haskell

Are you looking for the -ddump-splices flag to the compiler?

You may be able to use pprint or ppr from Language.Haskell.TH.Ppr (imported automatically with Language.Haskell.TH):

GHCi> expr <- runQ [| \f g x -> f (x*2 + 3) . g |]
GHCi> putStrLn $ pprint expr
\f_0 g_1 x_2 -> f_0 ((x_2 GHC.Num.* 2) GHC.Num.+ 3) GHC.Base.. g_1

It's not pretty, but it is valid Haskell. You should be able to make the output nicer by stripping off module prefixes from Prelude names (although you might need to be careful to only strip the expected prefix; Foo.* is a perfectly valid infix operator, after all).

As a complement to ehird answer:

Note that using runQ directly from GHCi in general might not work (e.g.: TH generators that use reify operations, cf. comments above the runQ declaration).

When that fails, you can pprint (or show), transform intro a string expression stringE then splice as an argument to putStrLn:

> putStrLn $(stringE . pprint =<< [| \f g x -> f (x*2 + 3) . g |])
\f_0 g_1 x_2 -> f_0 ((x_2 GHC.Num.* 2) GHC.Num.+ 3) GHC.Base.. g_1