Hi Bill,
A boat will drift sideways to the wind, although they all have a tendency to crab slightly towards the end of the boat on which the engine is mounted; so if your drift is not going quite where you expected, this may be the reason.
If the wind is over about 7 or 8 mph you may want to use a drogue to slow the drift of the boat. This is basically a parachute that is mounted to the upwind side of the boat and slows the drift speed of the boat by catching the water. Start by mounting the drogue roughly to the middle of the boat and then adjust it's mounting position using a G-Clamp if you find that the boat is not drifting square to the wind or crabbing.
Initially, don't be tempted by fancy drogue set-ups that you read about on here involving multiple mounting points. Keep it simple for your first few trips.
You need to stop the boat in an area upwind of the water you want to fish over. Start well upwind of the area you intend to fish over as it will give you plenty of time to get things squared away and set up ready to fish.
Always leave the engine in a condition that will allow you to start it straight away will a quick pull on the cord, as you may find you need to do this quickly if drifting into a bank. If the engine is a poor starter, then it may be a good idea to start it
before pulling in the drogue as this will give you some extra time.
When positioning the boat to start a drift, try and ensure that you have
fully stopped the boat, as it will carry on drifting nose-first for quite a distance if you are not using a drogue or are mounting one by more than one point.
The best way of fishing from a drifting boat (in my opinion) is to sit with the wind on your back and casting over the front of the boat. You will need to consider the drift speed of the boat when retrieving and increase your normal retrieve speed accordingly.
If the fish are lying fairly deep, you may need to change to a faster-sinking line in order to get your flies down to the correct depth before you drift over them.
Initially, you will find it more difficult fishing over the front of a drifting boat, but ultimately, more rewarding. It is a great method for finding fish on the bigger waters and, as the scenery is gradually changing, more interesting as well.
Don't expect to find fish everywhere, but initially (particularly on a new water) persist with longer drifts and you will find fish in areas you never expect to. On long drifts be prepared for periods of inactivity interspersed with frantic action as you drift over new fish.
If you see fish moving up ahead, don't be tempted to cast a full line to cover them as you are moving towards them anyway, and will be able to cover them better when you get closer.
I hope this helps to get you started and good luck!
Graham