It can seem like a miracle to get a sharp image of a troublesome subject. Sharpening post-capture is even more like smoke and mirrors. Looking sharp isn't easy.
To begin with, your images can only be as sharp as your lenses can resolve. Cheap lenses may save you money, but they can also significantly limit the sharpness of your images. When considering potentially comparable lenses, price may not directly correlate to sharpness, but it's certainly not unrelated. Saving a few bucks can cost you in the long run.
A low resolution camera can only capture low resolution images, and low resolution images are never all that sharp. Blow one up large enough to be useful and the problem becomes even more evident. Each pixel can record but a single value, so any fine details smaller than that will be irretrievably lost.
But camera resolution can cut both ways. While today's higher megapixel counts have given us the ability to render sharper images, they've also made it possible to see every flaw accurately in how those images were made. A less expensive lens may work well enough for a lower resolution sensor, but will show evidence of its price when used on a more capable camera. Everything shows more, both the good and the bad. Were we to enlarge otherwise identical images to the same size from a 10-megapixel camera and one with 20 megapixels, the images should be comparable. But few of us would be satisfied with that small comfort. Were you to buy a camera with more megapixels, you would naturally feel justified in expecting good results zoomed all the way in to 100%. I mean, if you buy more megapixels, you would want to see them all. But if your lens isn't up to the task, you may not like what you see zoomed in.
The same goes for your shooting technique. A slight camera movement during the exposure may not show on when captured by a lower resolution camera but could be quite obvious once you're able to inspect things more closely.
I often read able people unsatisfied with their new expensive camera, claiming that their old camera was somehow sharper. Perhaps a few did end up with a lemon but most simply found themselves confronted for the first time with the limits of their gear and their technique. It's like looking at the something with a more powerful magnifying glass. Given enough megapixels, whatever the weakest link is in your current system will become apparent. To look sharp with a high-resolution camera, you may need to up your game in more ways than just buying that new camera.
Optimal focus has to be part of achieving sharp images. Whether it be portraiture or high-powered macro photography, subjects with inherently shallow depth of field demand attention to detail when focusing. While it is possible with certain lenses and cameras to fine tune auto-focus, if you really care, there's no substitute for manual focusing. When I can and it matters, I'll use auto-focus to get in the ballpark, but then switch to manual focus to fine tune things. Not all subjects are forgiving enough to put up with such delays during shooting, but for those that are, it makes sense to double check.
It's tempting to believe that images can be sharpened post-capture to make up for softness introduced during shooting. To a degree, this is indeed true. Digital capture forces everything to conform to the overlay of a regular pixel grid, rounding corners and losing the precision of irregular edges. A small amount of sharpening in Lightroom or whatever your favorite app may be can help make things look sharper.
But sharpening post-capture can't sharpen what isn't there to begin with. A slightly softened edge can be made to look sharper to a degree. But there's little that can be done with an edge that is so blurred that it no longer deserves to be called one. Count on digital sharpening to help restore some clarity, but don't assume it can work miracles.
Yet all digital sharpening is somewhat of a slight of hand. It adds the appearance of sharpness by enhancing contrast along perceived edges. Rather than a somewhat indistinct blurry edge, sharpening makes one side of the divide brighter and the other darker. The added contrast makes the edge appear more distinct and thus sharper.
Sometimes people end up over-sharpening. Not you or me, of course, but one does hear stories. If a little looks good, they reason, a little more must be even better. Slowly but surely, they follow this logic to its conclusion. They creep their way ever sharper until the optical illusion at the heart of sharpening becomes obvious in the form of halos and fringes bordering high-contrast edges. Just check out any online photo sharing site if you don't believe me.
I always get a laugh when I see a movie or TV plot revolve around the police photo lab enlarging and sharpening a security camera image until they can identify the murderer based on his reflection in the diamond ring facets on the finger of his victim. Don't tell me you've never seen this sort of thing. For all its impossibility, it's a common trope. But alas, it doesn't really work that way. I think sometimes photographers come to put too much faith in digital sharpening. Perhaps they've been watching too much TV.
The bottom line is that there are no easy shortcuts to getting sharp images, either in the field or in the digital darkroom. Looking sharp requires paying attention to details. In order to look sharp you have to be sharp.
Well, we all do what we can.