I know that Simon is a really old new author, pardon the pun, but I don't understand all of the things he writes into his stories. In Plain english, I don't understand half of the references he makes since I'm only 16 and he's like 56. For example, in all of his books numerous characters all say some thing along the lines of "The old jokes are always the best" usually after saying something that makes very little gramatical sense. What exactly are these "old Jokes" and why have I never heard of them in my life? Also, in the nightside books taylor makes numerous jokes about "the maltese falcon" What is that? when I tried to look that up, all it was was an old detective movie that had very little to do with a bird at all.
Yeah, the references you're not catching are generally literary allusions. I had the same thing happen to me when I first checked the Nightside series out; I'd understand the references to Cthulhu or Arthurian legend, but miss the homage to Doctor Who or The King In Yellow. Now, however, it's one of my favorite things about his work; I'll reread one of the books every few months, and delight in all the Easter Eggs I missed the last time. As for the two things you asked about, here's the backstory:
The line "The old jokes are best" usually follows a demonic character saying something like "This is hell, nor am I out of it." Which in turn usually follows John or another character asking them "How is it thou art out of hell?" All of this is a nod to "The Tragical History of Doctor Faustus", a play written by Christopher Marlowe. The original work had Fausts summon the demon Mephistophilis out of hell, and ask "How comes it, then, that thou art out of hell?" Mephistophilis replies "Why, this is hell, nor am I out of it." The original point was that Mephistophilis, who had once been an angel and known the grace of heaven, considers anything else hell; damnation is not living in a fiery pit for eternity, but being severed from the connection to the Divine. In Green's novels, the answer becomes a joke for two reasons; first, because the character who originally asked how they came to be out of hell, they mean it literally. They literally want to know how they escaped hell. In answering with the Marlow quote, they're giving a non sequitor and elluding the question. Second, it's a commentary about the nature of the Nightside; how seedy and sordid it is.
The Maltese Falcon: Green usually namechecks it while having John Taylor say something like "I can find anyone or anything, but don't ask me to look for the Maltese Falcon". It's an homage to the novel "The Maltese Falcon", and it's later film adaptations. In the story, the plot revolves around detective Sam Spade dealing with a number of cutthroat people in search of the eponymous falcon, a priceless figurine. Over the course of the story, Spade is betrayed numerous time, and his partner gets murdered. When John Taylor refuses to look for it, he's saying that every attempt to find it leads to disaster, and he's not stupid enough to try. Simon Green keeps referencing it because the original novel by Dasheel Hammett, and the character of Sam Spade, were a great influence on Raymond Chandler's character Phillip Marlowe, and the genre of hard-boiled detective fiction in general. Since the Nightside books are at least obstensively detective novels, I imagine that Green has probably read more than his fair share of them, and threw the homage in to show his love. Hope I helped.