i usually eat something 30 min.-1 hr. before riding- something very light like a granola bar. immediately (i.e. 5 min. before start) before a race start i'll usually down some gel. for longer rides (beyond 60 miles, i'll usually carry two granola bars in addition to my gel flask and sometimes even a hunk of beef jerky)- you need protein on the longer ones.

it's really tough- everyone's need for warmup is different. i feel like garbage for 30 min. if i don't warmup. if you don't want to get there early- some techniques that kinda work are take a hot shower right before or use a warming embrocation. they both increase blood flow. they definitely will not work as well as a good warmup but it's better than nothing.

as spokes said, eat something immediately after your ride, preferably within 30 min.
as for training? make sure you spin out before your end your rides to flush out the lactic acid. part of warmup is the process of flushing residual lactic acid from previous rides. the less there is in your system when you start, the better. this is a technique that definitely works- during stage races, often there's a TT in the morning and a crit in the afternoon. it's critical to flush legs after the tt- makes for a much better race later in the day. same concept could apply here.