Racking your wires efficiently is a crucial part of quick and safe gear placements. If you are fumbling to find and deploy the right wire you are more likely to lose strength and be in an unprotected position for longer. There is also more danger that you'll drop them. Being able to manage them well is even more significant on longer routes where you are likely to be carrying extra sets......
Most people who attend our climbing courses after purchasing wires of their own present the whole set racked on to a single carabiner (they are often sold like this) but a bunch of 10 or 11 wires is hard to juggle half way up a tricky pitch. I much prefer to split sets into 2. On one biner I carry sizes 1-6 and on another I carry the larger sizes. I can usually estimate which size I need and even if I need to try a few I can certainly narrow it down to whether it's likely to be one of the larger sizes or the smaller ones. Separating them makes them easier to manage and it also has the advantage that if I drop them at least I will only lose half a set!
If I'm carrying 2 sets I choose a different wire type to offer a wider range of placement options (usually I take a set of DMM Wallnuts and a set of Wild Country Rocks). Again I rack half of each set on a different carabiner. It makes them so much easier to manage and although it means I'm carrying a few extra snap gates that has also occasionally proved useful when I've run short of crabs on a long pitch.
Finally, the type of carabiner you rack the wires on is worth considering too. Firstly, I would never recommend those tiny accessory carabiners. They are too small to handle efficiently with one hand and it makes far more sense to me to have a few extra full strength ones available if you need them.
Then the other consideration is what type of full strength crab to rack the wires on? Climbers have varying views on what shape works best. A friend of mine swears by oval shapes* as there are no angles and the wires slide around all parts of the the crab easily. There is also the question of what 'nose' shape works best (the part of the carabiner where the gate meets the main carabiner body). Some carabiners have a hook on the nose (shown in the left on the photo) and some have a blunt nose profile (shown on the right in the photo). Some feel the hooked style works best as the wires slide that far but then the hook catches them rather than them sliding off when you don't want them too. I have tried all types and my preference is definitely a D shaped carabiner with the 'clean nose' design. I accept that there is a risk an occasional wire might slide off but on the hook nose design the loop of the wire always seems to get hooked when I least want it too.
The important equation to remember is.....less fumbling x efficient racking = speedy deployment. Climbing is all about the maths :)
*There's lots more info on carabiner types available in our article 'The Carabiner Conundrum' here