Slick Changeovers on Chances
Efficient stance management is useful on long multi pitch routes as it saves time, giving you more time for climbing rather than faffing with ropes! It may also mean that you are off the route before darkness or the weather changes. Having safe simple systems that both you and your partner are familiar with is best. Here are some ideas
Have a plan and try to visualise the whole belay set up, second arriving, sorting gear and leader departing before actually doing anything! This can be a lot to consider initially but with experience will lead to efficient swap overs and time being saved.
As you arrive at the stance consider the best place for you to be standing in, try to make things as comfortable for yourself as possible. This will mean you are more relaxed and able to concentrate on what you are doing. Often though where you end up standing will be dictated by where the best gear placements are. Don't sacrifice safety for a comfortable stance! If you can take into account where the second will stand once they arrive and in what direction the leader will move off in, this will reduce the chance of rope twists and tangles allowing the whole process to go more smoothly.
Make good use of your time.
Whilst the second is putting on their rock boots or taking off a jacket you can be clipping the remains of the rack to an accessible place on the belay anchors (if the second is going to lead through). This is best done before the stance becomes crowded with a second or possibly a third person. Before you get the second to climb consider if you need to put an extra layer on, or get that chocolate bar out of your pocket - try and work out how long you might be standing on that ledge for!
Hopefully you will already have discussed this, know who will be leading off and therefore built an appropriate belay. If you are swapping leads then tying into the anchors with your ropes is the best method.
If you will be leading off again then equalising the anchors to a single point with slings would make your life easier when you swap roles.
Whilst belaying you can be planning how to make the second safe when they arrive.
If the second is going to lead through then you need to make them temporarily safe. This can be done most simply by tying an overhand knot on the bight in the dead rope.
There is no need to tie the plate off with a more complicated releasable knot as there should be no need to release it under load.
If you make the loop quite large you can then clip this into your tie-in loop to keep your partner safe whilst changing the orientation of the belay plate.
If you do not need to change the plate over then the overhand knot butted up against the belay plate is fine.
Once your partner is safe the rack can be sorted, the guidebook checked again and you can give them any useful information that you have gleaned from the route above, such as where the first runner is or a crucial hand hold.
Don't forget to take the nut key from them if you are sharing one.
Same person leading off again
In this situation the second needs to attach themselves to the belay and be in a position to belay the leader. If you have thought ahead and equalised the anchors to a single point then this is a simple process of attaching one screwgate. You may not have been able to set up an equalised anchor due to the position of the anchors or the gear that you have left. Maybe your second was planning to lead off but has had a change of heart now they have seen the next pitch and decides you should lead it. In this situation they will need to replicate the way you are tied in with their ropes. Make sure they clip in underneath your ropes to avoid any tangles.
The second can now run the rope through to ensure that it is the right way up for you leading off. It is worth taking a moment to do this now rather than finding yourself on the crux move with the belayer unable to pay out any slack due to a knot in the rope!