A)There are three different types of call whistle, exposed reed and rubber bulb. Stalkers have their favourites and swear that the rest are useless.
One of the cheapest and most versatile is the Hubertus, a whistle made of cherry wood with a screw to vary the pitch. Screw it in and you can imitate a fawns squeaks to bring a doe, hopefully with a buck in attendance. Ease it off and you get the does throatier peeping.
The Buttolo has a rubber bulb and is widely used. It is loud and can bring a buck in from a long range, but if used at full blast can scare anything close at hand. The best technique is to hide it in a pocket to muffle the sound. Press the bulb to its fullest extent and it makes a loud, agonised squeal, which will make a buck jump into sight or vanish at speed!
The third type, with an exposed reed, takes some mastering, but can not only produce the full range of roe sounds, but does so at varying loudnesses to suit the circumstances. Dont practice with a call in the woods it educates the deer. The British Deer Society shop (www.bds.org.uk) sells a CD on calling roe, priced £9.79.
I recommend that you keep your call on a loop of string attached with a safety pin so that it is handy but can be dropped in a hurry in exchange for the rifle. Fishing in pockets for a call while a buck is staring suspiciously at you is not good for your success rate.