Where a walk runs and what's under it matter more than how strong the concrete is. So before anything else, I look for roots, low spots and anywhere a car will cross, because those are the places a walk gets pushed around. When an old walk lifted or sank, we figure out what pushed it before we pour new, or the same thing tends to happen again.
The base is the part you won't see once we're done, which is exactly why it's the first thing that gets trimmed when a budget's tight. I'd rather keep the digging and packing and go simpler on the finish, because a nice surface on soft ground still cracks and sinks, and you can't fix the ground later without tearing the walk out.
A walk often ties into other concrete around the house. If the slab inside your garage is cracked or uneven too, we can talk about garage floor concrete on the same visit. If you'd like the walk to have color or a pattern instead of plain gray, that's decorative concrete, and we'll go over how it holds up underfoot.
Concrete shrinks as it dries, so some cracking is normal. Control joints are the grooves we cut across the walk to give it a planned place to crack, in a straight line down in the groove. Cut late or skipped, they leave cracks wandering wherever the slab chooses, so we mark where they go before the pour and cut them on time.