We're talking Saturdays, especially in the summer, where the dock is full and you're right next to boats on either side. Pretty normal, and we teach it. Back out, using a backed main or not, tiller centered until you clear the other boats, then steer the stern toward the sea wall (want to go to Emeryville? tiller to Emeryville). Power up the main and go.
I did a "Between the Docks" workshop recently, where we covered all of the bad things that can happen on launching or docking, how to prevent them, and how to handle them when they happen (and they will, to the best of us).
What you want to avoid is heading out in the wrong direction, toward the sea wall instead of Emeryville. It happens at times, but how does this happen? Clearly, you get turned the wrong way backing out of the dock. But other than complete misuse of the tiller, what contributes to this?
As always, I learn a lot when I teach, and I picked up some critical points in this workshop, watching the students go through their launching/docking/heading for the sea wall drills. The points all fall into the "obvious when you think about them or have them pointed out, but not obvious earlier". So I hope these fall into that category for you.
Here are some things to consider.
First is the angle of the boat to the wind as you push off. Normally it is pointed into the wind, more or less, but it moves around. The position it is in when you push off will increase or decrease your chances of heading toward the sea wall. If you have a slight angle like this
you're more likely to go to the sea wall, where with an angle like this
you're more likely to go out the way you want, toward Emeryville.
So just take the time to align the boat a few degrees in the right direction.
Another thing is backing the main to move you backwards. You don't have to do it, as with any reasonable amount of wind, the wind against the hull of the boat will move it backwards without additional help. Backing the main will move it faster, and it may be necessary in very light wind, but you may not want to go faster if you're single-handing and getting control of the boat as you step on board.
But on which side do you push the main out? Backing the main will move the boat backwards, but it will also push the bow out one way or the other. If you back the main to starboard, it will push the bow out to port and vice versa. At low boat speeds going away from the dock, you can counter this effect easily with the tiller/rudder, but why fight it? Back the main to starboard to push the bow out in the direction you want it to go.
And push the sail out all the way, to the shrouds. If you don't, the sail will power up going forward at a certain point, which is not what you want.
What I saw in the workshop was something we don't usually think about but we should, and it is critical - weight positioning. I saw skippers sailing backwards, trying hard to steer the stern toward the sea wall with the rudder, but it wasn't happening because their weight was to starboard, where they would have to be once the boat powered up going toward Emeryville. But backing out, this lean was steering the stern to port. So the lean of the boat was fighting the tiller, and it was winning. How you lean the boat is really the most important thing, more important than the angle of the boat to the dock or to which side you back the mainsail.
This is why we teach rudder-less sailing. You understand all of the things that make the boat move or turn and how to use them effectively, with or without a rudder. One of them is boat lean (your control is where you put your weight). If the starboard side of the boat is low, the boat will turn to port, going forward or backward. Naturally, as you leave the dock, you want to be on the starboard side anticipating a starboard tack out to balance the wind. But backing out of the dock, this turns the boat the wrong way, so you need to be either neutral or weight to port backing out.
I taught sea kayaking for 10 years, and my kayak did not have a rudder. The principle of leaning the boat to turn is the same, but you visualize it differently. If you want to go left, you lift your left knee, dropping the right side of the boat into the water, and turning left. Same thing here, but different body mechanics and mental image.
An interesting aspect of this is what you do as an instructor. I see a lot of instructors do "dry run" launching, having the student go through the tiller moves with the instuctor holding on to the bow line (maybe with an extension to the bow line to let them really get out there). This is a fantastic method, as it allows the student to practice the movements safely before doing them for real. I'll add one thing here. When I teach beginners, I launch them, step on forward of the mast, and stay they until we're clearly going out. It is very rare that we get into a circumstance where I have to take the tiller, and I want it to be rare, as I want to coach the student through whatever is happening, calmly. And usually I can. But from my position forward of the mast, I can help them by using my weight, more easily and effectively than if I were aft of the mast in the cockpit. I can lean the boat quite a bit by putting my weight full on one leg or the other, and that turns the boat.
Some small but important points. Hope they help.
And I would encourage you to take this workshop, which we will be offering more often.