There is probably no "one-size-fits-all" technique that works for everyone, nor universal criteria for writing good song parodies, but I'm going to share the techniques that have worked for me. Since 1995 (with a 2 year gap between 1996-1998), I've written over 700 song parodies, about 99% of them political satire. The basic difference between writing musical political satire and other types of song parodies is that the target of ridicule is not the song itself, but politicians. There is also the issue of audience familiarity with not only the original song, but with the political issue/personalities being targeted. So, in my attempt to reach both groups (politically active audience members and music/parody lovers who may be unfamiliar with current political events), I make sure that my parody lyrics sound familiar, are as easy to sing as the original songs (referred to as good "pacing" at AmIRight) and, if possible, have matching MIDI music for singing along with the lyrics.
1. Pick a familiar song. A good song parody depends upon familiarity of the song relative to your audience. Therefore, it's not a good idea to write a parody of a really obscure song; very few will recognize it.
2. Stay true to the original lyrics. While it's much easier to completely re-write your own lyrics and rhymes, wherever possible, I try to preserve as much of the original rhyme as I can when writing my parody lyrics. (When it's impossible to find a matching rhyme, you can still approximate it with the same vowel sound at the end of a lyric line.) The better the audience knows the lyrics of the original song, the more they can appreciate subtle humor, especially if you are writing satire. Sometimes all you need is to substitute a word here or there. Here are some of my favorite opening lines (parody lyrics in parentheses):
From "The Christmas Song":
Chestnuts roasting on an open fire
(Gun nuts boasting they will open fire)
From "Black Water" by the Doobie Brothers:
Well I built me a raft, and it's ready for floating
(Well he gave us the shaft, and already he's gloating)
From "You're So Vain" by Carly Simon:
You walked into the party like you were walking into a yacht
(You're leader of the party of all the fat cats who own the yachts)
From "Today" by the New Christy Minstrels:
Today, while the flowers still cling to the vine
(DeLay has the power to sling all his slime)
From "Your Love Lifts Me Higher And Higher" by Jackie Wilson:
Your love is lifting me higher
(He's Rush, the shifty big liar)
3. Parody lyrics should be easy to sing. A good song parody should ideally be as easy to sing as the original song lyrics; the parody lyrics should flow well with the music. When writing your parody lyrics, imagine the original singer singing your song parody on stage - would that singer trip over the parody lyrics that you've written? When writing, you need to be careful to count syllables and watch for awkward accents caused by certain placements of lyrics. So, you may need re-write your lyrics with other synomyms.
4. Start from the complete original lyrics. To avoid mistakes of recollection, I usually work from the original lyrics, which I later match up with a MIDI music file. Fortunately, you don't have to own a personal library of music books, you can simply go to the Internet. My favorite lyrics web site is Lyrics World, a huge and well-organized site run by Paolo Filho, based in Brazil.
http://www.ntl.matrix.com.br/pfilho/html/main_index/
You can find just about any pop or rock and roll song lyric there.
What if you want to write a parody of a folk or non-pop song?
You can find lyrics to most folk and traditional songs at the Mudcat folk/blues web site.
Do you want to try writing a parody of songs from Broadway musicals?
Try the Musical Heaven web site for these type of lyrics.
You can also use the Google search engine to find lyrics - type in the name of the song followed by the word "lyrics."
5. If you use MIDI accompaniment, match your lyrics to the MIDI music. There may be many versions of the same song, composed by various MIDI musicians. Compare and test several versions of a MIDI file to find the arrangement you like best. I usually choose an arrangement closest to the original recording of the song. Then, make sure your parody lyrics and verses are structured to match that particular MIDI arrangement. A really fast way to find a MIDI file on the Web is to use MIDI Explorer, a search engine created specifically to scour the Web for MIDI files.
MIDI Explorer - http://www.musicrobot.com
For MIDI files from Broadway musicals, try the Broadway MIDI site.
6. It happens to all writers... creative drought, and forgotten ideas. To minimize creative drought, stay organized, and keep a small notepad and pencil handy to jot down parody ideas as they occur to you. (I usually jot down the name of the original song that I want to parody, and I sometimes come up with a new title.) Then, download and print out the lyrics on separate sheets and pencil in any parody lyrics that you may come up with. You can build up a collection of parody candidate titles that way. I usually come up with parody titles and write them down. From time to time, I will flip through the lyric sheets to see which one I might be able to finish. Sometimes, current events or new ideas will supply the spark for finishing a parody that have been languishing.