My garden is so full of plants already that I am wondering where I will put all of the new plants that I, of course, want to buy this year.
One trick is to prune some of the overgrown bushes so that new items can be tucked into unveiled spots. Of course, I always put slow release fertilizer in those holes as bushes take a lot of the goodness from the surrounding soil.
Sometimes, I have to wait awhile before planting a new item, as it takes some time to walk around and ponder the options. But if I have two of a particular plant, I usually put one in a different part of the garden from the other and watch to see which location works out best over time.
I used to rush to get everything planted as soon as I arrived home from a nursery or plant swap, but now I am more likely to take my time and keep a few pots in reserve for later. I have a space in filtered shade where I keep my reserve stash. This comes in handy to replace plants that suddenly die and/or to fill in space that becomes available after I weed or divide plants that have overtaken a bed.
Digging out surplus perennial plants is easiest in the spring when they are still small and when the ground is usually moist. It is an ideal time to take extras to a swap or pass them along to another gardener. Gardening is made up of a lot of acquisitions and dispersals.