In reply to two_tapirs:
I think on my first lead, I had 2 wires pop out. Since then, I don't think I've ever had more than 2 pieces of gear come out on a route. The vast majority of my routes, none of my gear will fall out, although when I've had falls, some of it has zippered out (always low-down nuts).
General tips to avoid gear coming out:
- Get familiar with the concept of the force on a piece of gear being at the bisection of the angle of the rope through it when taut. Visualize this whenever you are climbing.
- Properly extend any key pieces. It's often better to fall a guaranteed extra 60 centimetres than to risk having the gear coming out and then falling an extra 6 metres. Be careful extending too much at the bottom of the route, and around ledges however.
- Place an early cam (or other multi-directional piece, such as a thread, or deep-seated hex/nut). These will prevent zippering, as they can sustain upwards force and "protect" the upper gear from this upwards force.
- If a sling or nut could be pulled out as it's a bit loose, you can weight the placement with a big hex/cam to help keep it in.
- If a placement must not fail, there's nothing wrong with building a mini-belay mid-route (unless it's in a place where it's too pumpy). You can use screwgates here too for extra security (I often do on pegs).
- Get your belayer to stand as close in to the route as possible. However it's a trade-off between being hit my detritus/falling climbers/having good vis and zippering the gear out.
- A trick I use is to have 2x revolver wiregate slingdraws, and I place these on any "rope corners". If placed correctly they can heavily reduce rope drag, and this helps to keep gear in.
- If you are going to place a shit piece of gear (usually I do this only as a psychological thing, or to "get into the zone of placing and clipping gear") - tell your belayer that you've put a shit piece in, and why. This helps to allay any fears or doubts about your ability to be safe when it inevitably comes out, or if your belayer discovers a cosmetically placed nut.
- If you need to put crucial gear in to protect a crux, but you'd get too pumped getting it in - considering placing it properly then down-climbing to a rest before doing the crux. In other words there's sometimes no need to try and place gear and go for the crux in one go, when you can place a bomber gear, rest up for 5 mins then do the crux.
Hope some of that helps