I have flipped over my hub to try out the fixed wheel for a change, I am finding it very difficult to keep balanced while attempting to ride backwards! Does anyone have some advice or is there any trick to learning how to go backwards?
Bicycles are designed in a way that makes them very stable going forward, at the cost of being unbelievably unstable while riding backwards. The most common fixed-gear geometry (inspired in track racing) doesn't help a lot. As a comparison, BMX is a modality where riders usually ride backwards in half-pipes, but the bike geometry is very different.
What I tried to do (before giving up), and what I have seen people doing, is to try to ride backwards IN CIRCLES, perhaps lowering the saddle a bit to a more relaxed position. I don't think the clipless or toestraps are key here, but a lower gear ratio might be very helpful.
After you perform some circle attempts, you can try to switch sides. Trying to do it very slow aids to gain inside as to which movement you actually have to do, since this movement is very counterintuitive: when you are leaning SLIGHTLY to one side, you have to point the handlebar the opposite way, so that the bike will go under you again.
I could manage to go some 4 meters back when I was trying often, but with almost no control over the direction the bike was going.
Perhaps a good video to start (with interesting links on the sidebar) is this:
Hope this helps!
From my experiences with going backwards(fakie) on BMX, the best way to learn is to find a small bank or quarter pipe, ride up it, and come back down backwards. This will give you that initial speed so you don't fall over right away. I imagine it'd be kind of similar on a fixed gear, expect that you can actually gain more speed by pedaling backwards. I think the roll out would be similar.
Flip it back to non-fixed and get the hang of rolling backwards (perhaps down a gentle slope) first. As others have said, the bike is designed for going forwards, so backwards is a real skill. So you've got two major problems - steering and locomotion.
Do you drive? Almost all non-4x4 vehicles are front-wheel steered and reversing any distance in a straight line is similarly tricky. If you've driven a rear-wheel steered vehicle, perhaps a tractor or a forked lift, you'll know that they can be really maneuverable in tight spaces but quite tricky to keep in a straight line when going forwards.
It is though all about practice. 10000 hours to be world class!
Once you can roll backwards unpowered, then try the rolling backwards with the fixed, you'll at least have conquered the steering problem, now you can mix in the locomotion.
Get some clipless pedals. Then, practice until you feel like you've been practicing all day, then practice some more. Continue to practice until you're successful.