Formal structure of  "Day Tripper":
Intro (trans.) 0:00-0:18*
Verse 1 0:18-0:46
Verse 2 0:53-1:21
Verse 3 1:49-2:17
Coda (trans.) 2:31-2:46
Comments: Many Beatles recordings to date used two-part intros in which a single instrument starts, then after a few seconds the rest of the band joins in ([6b] "A Taste Of Honey",  "Thank You Girl",  "Little Child", [14b] "Roll Over Beethoven",  "You Can't Do That", and [31b] "Matchbox",  "Baby's in Black", [38b] "Mr. Moonlight",  "I Feel Fine", [46e] "Honey Don't",  "Ticket to Ride", and  "Run For Your Life"). "Day Tripper" is similar, but doubles the intro into four parts: first we hear a lone guitar, then it's joined by the bass, followed shortly by the tambourine, and then finally the drum set.
"Day Tripper" is the first Beatles recording to use and introduction based on transitional material, and also the first to use a coda likewise based on transitional material. In this case, that means the famous opening guitar lick, which functions as "musical glue" connecting the various formal components.
The Trans./Break/Solo employs elements of all three, so exactly what to call it is uncertain - it really is a mix of all three.
The verses employ a modified 12 bar blues structure. For more detailed analysis on that aspect, read my 14 January 2013 blog.
This blog is a workshop for developing my analyses of The Beatles' music.