In reply to Stone Muppet:
Do you mean when you have to keep switching between moving together and doing short pitches? That's always a pain.
Main thing is get good at taking and dropping coils quickly as you'll be doing a lot of that.
Block lead when short pitching as the leader keep most of the gear and is good to go as soon as the second arrives and restacks the rope. Even with longer pitches it often comes down to who's got most of the gear.
Try to judge how much rope you'll need. Leader carries a 'reservoir' of a few coils in case more rope is needed - this can be dropped quickly if need be, including if the pitch is a bit spicy and the leader doesn't want to climb with coils.
Get efficient at bringing up the second, preferably using guide mode off a power point (in situ, sling round a block, 2-3 pieces of gear equalised with a sling or two). That way you can scope up the next pitch and have a drink etc while belaying and it makes changeovers quicker.
If the leader has dropped the reservoir and can see that less rope is needed for the next pitch / moving together section, they may be able to start taking coils while belaying in guide mode but that's a bit tricky considering you always want one hand on the dead rope even with a guide plate. If the second has stopped to do something like fighting to get a piece of gear out (place gear which is easy to remove!), stick an overhand knot in the dead rope and you can then use both hands to do whatever but ask the second to give you a shout when they're read to move off again to avoid excess slack.
As leader, position yourself on the side of the belay where you're going to move off to for the next pitch. Eg moving right, be on the right hand side. Second arrives at the belay, positions on the left hand side so you don't have to climb round them.
Have a free screwgate ready on the powerpoint before the second arrives and clove hitch them onto it using the dead rope from the guide plate and take the guide plate off. Meanwhile the second is already busy restacking the rope. Or the second can use a pre-attached lanyard with a pre-prepared screwgate on the free end and clip to the powerpoint with that. What you don't want is the second faffing around with getting a screwgate, clove hitching themselves on and removing the guide plate.
Basically on stances make sure both climbers are always doing something. If they aren't, that's inefficient. If neither person is doing anything, that's dead time. Same principle applies with abseiling, except that you can save even more time there.
Probably lots of other things I've missed. The real answer is there's no substitute for getting out there and experimenting and/or going with someone more experienced...