I have a trip to Turkey coming up and want to avoid jetlag as much as possible. Is it better to stop in the middle for a day's break to give my body time to adjust, or would it be better to get it all over with at once?
Breaking the trip into two legs with brief rest in between is widely recommended by sleep experts as a way to reduce jetlag.
If the trip is just a day or two, shifting your circadian rhythms that quickly is impossible and your best bet is coffee and muddling through as best you can.
On long trips you have plenty of options. The most effective, and most bothersome, technique to avoid jetlag is to shift your sleep times gradually over several weeks to match your destination. That would require a lot of time and dedication.
A more practical tip is to take 5mg melatonin at bedtime for several days once you reach your destination. Melatonin is the main hormone responsible for regulating the body clock and it's been shown in several good studies to very effectively speed the adjustment of the body's circadian clock.