stefo2 once bubbled...
The weather should be nice and sunny, day time temperatures in the mid 20s, water temperatures around 23°. It gets cool at night, also the wind chill effect can be very strong there, so bring sometihing warm for the evenings and for after the dive, especially in the afternoon.
As for dive sites - the best ones are in Ras<Mohammed and in the Straight of Tiran, however, most (if not all) diveshops will have you do locl dives first.
Check the other threads below on Sharm - some detailed trip reports.