Start with the ihram
Two sets, not one. The first will be worn, washed and worn again, and having a dry spare after a rain shower in Makkah is worth the small amount of space it takes. Men should pack a seamless belt with a zip pocket for cash and a copy of the passport.
Clothing
Makkah and Madinah are hot for most of the year but hotel air conditioning is aggressive. Pack light cotton for daytime and one light layer for the lobby and coaches. Five changes is enough for a fourteen-night trip if you use the hotel laundry once.
Footwear
The single most common mistake is new sandals. Bring a pair you have already worn for at least a week, plus a cloth drawstring bag to carry them into the Haram — shoe racks fill up and finding yours afterwards in a crowd of thousands is its own small pilgrimage.
Medicine
Bring paracetamol, rehydration salts, throat lozenges, plasters and any prescription medicine in its original packaging with the prescription itself. Pharmacies in both cities are excellent, but not at two in the morning when you have a headache.
Documents
Passport, visa printout, vaccination certificate, four spare photographs, and photocopies of all of it kept separately from the originals. Photograph everything and email it to yourself as well.
What to leave behind
Scented soap, deodorant and toothpaste while in ihram. Large suitcases — most groups have a strict allowance and the coach holds fill quickly. And expensive jewellery, which spends the trip worrying you.