Start dividing perennials now, before they get too big. Day lilies, hosta, and some of the Siberia irises are showing good growth but demonstrating how crowded they are. Stick a shovel under them to pop up the whole bunch, then carefully separate them by hand. The Siberian iris are different than the bearded iris and easier to divide because they are growing from individual bulbs. Bearded iris roots (actually, rhizomes), on the other hand, look like a bunch of lobsters that got a little too friendly. These need to be gently pried apart before you can replant them. Not sure which is which? Do a web search of "Van Gogh iris" and you'll see a magnificent representation of the bearded iris; do "Monet iris" and you'll get a very good picture of the Siberian type.
Hit up the garden store (not big box). Because the calendar and the weather are so in conflict with each other, it's a good idea to do your shopping at a nursery. Box stores, although they will often have quality merchandise, are in the business of selling you on impulse. They will sell you tomatoes in April to plant on that random 80-degree day, and then they will resell you the same kind of plant at the proper time to replant the ones that died. Independent garden center folks are much more apt to give you the right planting times when you buy your seeds and transplants. Hint: It's still too soon to plant tomatoes.
Take a walk. Look around the neighborhood to take in all the beautiful blooming stuff; list the things you particularly like and the date you saw them blooming, and consider working them into your landscape in future years.