Most pruning mistakes are timing mistakes, not technique mistakes. The cut itself was fine — it just happened in the wrong month, and the plant answered by not flowering. Almost all of it comes down to one question about the plant in front of you.
The one question that covers most shrubs
Does it flower before roughly the end of May, or after? Spring bloomers — azalea, forsythia, loropetalum, spirea, most camellias — set their buds the previous year on old wood. They get pruned right after they finish flowering. Wait, and you are cutting off next spring's display.
Summer bloomers — crape myrtle, abelia, panicle hydrangea, rose of Sharon — flower on wood they grow in the same season. They get pruned in late winter, while dormant, and there is still a full year of growth ahead to make the flowers.
Late winter is for the hardwoods
February into early March is the window for structural work on deciduous trees around here. The leaves are off, so the framework is visible; the tree is dormant, so it isn't losing stored energy; and the wound has the whole growing season ahead to seal over.
It is also the wrong time to do the thing crape myrtles get done to them every year. Cutting the trunks back to knuckles doesn't make more flowers — it makes weak, whippy shoots off a scarred stub and destroys the bark and branch structure that is the best thing about the plant. Thin out crossing and inward growth instead, and take whole branches back to where they start.
Palms: take less than you think
The instinct with a palm is to take everything that isn't perfectly green, and it is the wrong instinct. A palm pulls nutrients back out of a fading frond, and it has no way to thicken its trunk to compensate for what it loses. Over-trimmed palms narrow, weaken and get more storm-vulnerable, not less.
Take the fronds that are fully brown and dead, plus the old fruit and flower stalks. Leave anything still holding green. The severe cut that leaves a handful of fronds pointing straight up is popular and is genuinely bad for the plant.
Deadwood is the year-round exception
Dead, damaged and diseased wood comes out whenever you find it. There is no season for it — the wood is already gone, it is not going to recover, and leaving it up is a hazard and an invitation to insects and decay.
The same applies to anything that has become a safety problem: a limb rubbing the roof, a branch blocking sight lines at the end of a drive, a low limb over a walk. Timing theory is for healthy growth you are shaping. Hazards get dealt with when they appear.
Rather we handled it?
Tell us what the property needs and we'll come and look. Monday–Saturday, 7 AM–6 PM.